CA2187213A1 - Junction splitters consisting of channel waveguides and applications - Google Patents

Abstract

An integrated optical combination splitting device, in particular for applications in the wavelength range of visible light, which ensures a spatial, broadband concentration of light in a wavelength range .DELTA..lambda. greater than approximately 75 nm (valid for short-wave visible light). For a useful wavelength range comprising all visible light, a white-light splitting device is provided. The combination splitting device consists of at least three strip waveguides, at least one of which being a single-mode integrated optical broadband strip waveguide (EOBSW). Two strip waveguides (2, 3) each have an entry point (E1, E2) and are joined at their exit points (A1, A2) in a coupling point (6) to become a joint EOBSW (5) having a common light exit (AM) at its end. This broadband combination splitting device can be used as a wavelength-selective or wavelength-independent switch or modulator in interferometric and photometric arrangements, sensors and microsystem solutions.

Description

19503 930.0-S 1 X 9597 ~., Pti3 I.i l~ . 2 1 ~ 72 1 ~
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Descrlptlon 1. Desi~nation of the Invention Junction Splitters consisting of Channel Waveguides and Applications

2. Teclmical Area The invel~tion concerns a jlmction splitter used for the spatial combination or splitting of light of different wavelengths or different wavelength ranges from a comparably large wavelength spectrum. If required, this wideband junction splitter is used to switch, deviate, or modulate light.
The invention also provides for applications of this wideband junction splitter.The singlemode channel waveguides used for the wideband junction splitter are singlemode integrated-optical wideband channel waveguides or white light channel waveguides described in the patent application "Channel Waveguide and Applicatiolls" submitted on the same day.
The invention is also related to the patent application "Colour Image GenerationSystems and Applications".

For the purposes of this document, light refers to visible and invisible (infrared and ultraviolet) electromagnetic radiation, in particular however discrete wavelengths or wavelength ranges of visible radiation in the wavelength spectrumfrom 400 nm to 760 nm. The designation "channel waveguide" is applied to waveguides based on the principle of the total reflection of light, caused by anincrease in the refractive index within the waveguiding region in relation to the surrounding medium.

2 1 8 7 2 1 3 2 19503 930.0-51 X 9597

3 State of the Art J~mction splitters for a bandwidth less than 95 mn (value given applies to short-wave visible light) are known. The combination of discrete channel waveguides iseffected for the purpose of combining light according to the basically known principle of two-mode intelrerellce by:
- using a Yjunction coupler - using an integrated-optical switching or distribution element such as X-couplers, directional couplers, three-guide couplers, or BOA
(see ~ Kalthe, R. Mulle~; Infegrierte Optik f~nfegrated Opfics), Akademische Verlagsgesellscha~ Geest & Portig K-G., Leipzig, 1991 and A. Neyer:
'-Infegriert-Optische Komponenten fiir die Optische Nachrichtentechnik"
(lntegrated-Optical Components for Optical Communications Technology), habilitation thesis, University of Dorhmund 1990 ).
BOA is a French language designation (bifurcation optique active) for a group ofintegrated-optical devices ~see: M. Papuchon, A. Roy, D.B. Ostrowsky, "Electricallyactiveopticalbifurcation:BOA~, Appl. Phys. Lett., Vol. 31 (1977) pp. 266-267).

The efficlency of Junctlon-spllttmg - m addltlon to the slmultaneous requlrementfor efficient modulation and/or switching of the light - is dependent on the channel waveguides that provide the inputs and outputs of the junction splitter being in singlemode. The known channel waveguides for wavelength ranges with a bandwidth greater than approximately 130 nm (value given applies to short-wave visible light) are not singlemode.

Different light wavelengths require different values of the characteristic channel waveguide parameters such as the refractive index of the substrate, refractive 2 1 8 7 2 1 3 3 19503 930.0-Sl X 9597 index of the superstrate, refractive index or one- or two-dimensional refractiveindex profile of the channel waveguide, cross-sectional shape (e.g. width and depth), and channel waveguide position in or on the substrate. In general, this requires the use of different channel waveguides for different wavelengths of the guided light.

In the case of a junction splitting on the basis of known channel waveguides, e.g.
the titanium-indiffused chaImel waveguide in LiNbO3, the usable wavelength rallge reduces by approximately 35 nm, when compared against the wavelength range of the associated singlemode channel waveguide, as in junction splitters based on two-mode interference such as Yjunction couplers, directional couplers, three-guide couplers, X-couplers, or BOA, the oscillation build-up of the second mode in lateral direction in the j~mction or splitting area must be avoided. This is the precondition for a constant splitting ratio of the light tr~n.cmi~sion performance for junction splitter operation across the entire usable wavelength range.

To achieve efficient junction splitting of light from a wavelength range greater 95 nm, it is thus necessary to use one and the same singlemode channel waveguide which, from a technical point of view, transmits efficiently all wavelengths with a bandwidth greater than 130 nm approximately ~value given applies to short-wave visible light). Transmission with a technically sufficient degree of effectiveness means that the effective refractive index Neff of the mode guided in the channelwaveguide must be at least 5x10-5 above the refractive index of the surrounding material ns. This is a necessaly precondition for achieving low values of waveguide attenuation in the range 1 dB/cm. Technically effective signifies furthermore that, in the entire singlemode guidable wavelength range, waveguide 2 1 ~ 7 2 1 3 ~ 19503 930.0-51 X 9597 attenuation and the efficiency of a coupling between the channel waveguide and asinglemode optical fibre should not change by more than 30%, as light is usuallycoupled into the channel waveguide by means of singlemode optical fibres.
Using standard channel waveguides~ it is not possible to guide e.g. red and bluelight in one and the same channel waveguide in singlemode and with a technicallysufficient degree of effectiveness.

There is so far no known device which allows light of different wavelengths witha bandwidth greater than approximately 95 nm (~value given applies to short-wavevisible light), in one and the same waveguide structure, to be guided in singlemode as well as, if required, to be efficiently modulated, deviated, switched, and spatially combined or split, either separately or in combination.

To this end, requirements must be met which in this form, and in combination with known modulation mech~ni~m~ such as ~Itili7ing the electro-optical effect, have not yet been implemented.

According to patent application DE 43 27 103 Al, an interferometricallyadjustable optical filter is known. The optical filter splits an input signal into several waveguide branches. In each branch, the amplitude and the phase of the signal will be individually controlled. The signals will then be recombined in a wavegulde.
The filter element serves as a demultiplexer for wavelength multiplex operation in teleco~ nul~ications technology at wavelengths between 800 nm and 1.6 ,um, and with a comparatively narrow bandwidth.

4. Task of the Invention `-- 21 8721 3 5 19503930.0-51X9597 This present invention is based on the task to combine spatially, or to split, light beams from a wide wavelength spectrum or from several discrete wavelengths with a large wavelength distance; and, if required, to modulate, deviate, and/orswitch these light beams before or after, or at the point of, such spatial combination. The beam is to contain light from several wavelengths or wavelength ranges, in particular all wavelengths or certain wavelengths of a bandwidth ~ ~ 95 llm from the visible light spectrum. For implementing wideband junction splitters, this means that there is also a requirement for wideband chamlel waveguides featuring a singlemode guidable wavelength range of at least 130 nm (value given applies to short-wave visible light).

For the wideballd junction splitter, basically known areas of application are to be developed such that a comparatively simple construction of optical assemblies and devices becomes possible. The possibility is to be created to produce integrated-optical devices which are capable of tr~n~mitting in singlemode, modulating, and/or junction-splitting (splitting spatially or combining spatially) light across a wide wavelength spectrum.

5. Si~nificance of the Invention According to the invention, the problem is solved by means of a junction splitter comprising channel waveguides with the features of Principal Claim 1.
The sub-claims 2 to 6 characterize geometric and optical applications of the junction splitter in accordance with the features of Principal Claim 1.
The sub-claims 7 to 20 are advantageous further applications of Principal Claim 1. According to the invention, wideband junction splitter applications areeffected pursuant to the features of Claims 21, 22, 23, 27, 34, or 35.
The sub-claims 24 to 26 represent further applications of the Principal Claim 23.

2 1 8 72 ~ 3 19503 930.0-51 X9597 The sub-claims 28 to 33 represent further applications of the Principal Claim 27.
The sub-claim 36 represents a further application of the Principal Claim 35.
-According to the invention, at least two singlemode integrated-optical channel waveguides - which do not necessarily need to be, but advantageously should be, wideband - will be combined such that a subsequent singlemode integrated-optical wideband channel waveguide, hereinafter designated as SOWCW, will pass on the spatially combined light. The SOWCW is designed according to the patent application "Channel Waveguide and Applications" submitted on the same day.

This SOWCW is capable of wide bandwidth and singlemode light tr~n~mi~sion.
Wide bandwidth signifies that the radiation of different wavelengths, in particular of the visible light spectrum, with a bandwidth of > 0.48 x ~ - 85 nm (where ~ and ~w are stated in mn) can be transmitted in singlemode with a technically sufficient degree of effectiveness.
For visible light, this means e.g. a SOWCW bandwith greater than approximately 105 nm in relation to the wavelength ~ = 400 nm, and a SOWCW bandwidth greater than 130 nm in relation to ~ = 450 nm (Figure 6b).

Singlemode means that for each given wavelength within a wavelength range one and only one effective refractive index, namely the effective refractive index Noo of the fundamental mode in the SOWCW, can be allocated (Figure 6a).

- 21u7213 19503930.0-51X9597 Normally, and thus in these documents also, the mode order count starts at zero,e.g. fundamental mode Noo, first lateral mode Nol, and so on.

Light is ~mderstood here as meaning visible and invisible ( infrared and ultraviolet) electromagnetic radiation. Tr~n~mission with a technically sufficient degree of effectiveness means that the effective refractive illdex Neff of the mode guided in the SOWCW must be at least Sx] 0~5 above the refractive index of the surrounding material ns, where nS designates the value of the substrate index nl or the value of the superstrate index n3 - whichever is higher. This is a necessaryprecondition for achieving low values of waveguide attenuation in the range l dB/cm and implementing a channel waveguide such that it can be used efficiently in teclmical applications.
For each given wavelength in the range between ~a and ~a+~w, one and only one effective refractive index, that is the effective refractive index of the fundamental mode Noo, can be allocated. The singlemode range is determined on the one hand by the efficient oscillation build-up, from a technical point of view, of the fundamental mode Noo at wavelength ~a+~w, and on the other hand by the efficient oscillation build-up, from a technical point of view, of the first mode in a lateral direction Nol or the first mode in depth direction Nlo at wavelength ;~a. The values of ;~a and ~a+A~ are determined by the geometric/substance parameters of the channel waveguide and the media surrounding the channel waveguide. ln principle, the ~ Um value of the usable wavelength ~,"n and the m~imum value of the usable wavelength ~ax are determined by the optical tr~n~mi~sion range of the materials used.
For the crystalline material KTiOPO4, for example, the minimum value of the tr~n~mi~sion range is approximately 350 nm, and the maxin~ value approximately 4 ~m.

21~7213 -- 1 9503 930.0-5 1 X 9597 Technically effective signifies filrthermore that, in the entire singlemode guidable wavelength range, waveguide attenuation and the efficiency of the optical - coupling between the SOWCW and a singlemode optical fibre should not change by more than 30%, as light is usually coupled into the SOWCW by means of singlemode optical fibres. Using standard channel waveguides, it is not possibleto guide e.g. red and blue light in one and the same channel waveguide in singlemode and with a technically sufficient degree of effectiveness. The SOWCW parameters substrate refractive index, superstrate refractive index, refractive index or one- or two-dimensional refractive index profile of the SOWCW, cross-sectional shape (width and depth, for example) and the location of the SOWCW in or on the substrate are dimensioned such that across a wide wavelength range, in particular across the entire visible light range, singlemode operation of the SOWCW is ensured (see general dimensioning regulations for integrated-optical channel waveguides in: ~ Kart~e, R. Muller, ~ntegrated Optics, Akademische Verlagsgesellschaff Geestc~PortigK-G., Leipzig, 1991).
In particular, light waves of the entire visible wavelength spectrum can be guided.
Such light wave guidance in one and the same SOWCW across the entire visible spectrum will be in singlemode and, from a technical point of view, of the sarneeffectiveness. Thus, this is a real singlemode white light channel waveguide.

The SOWCW according to this invention are characterized by the specifically adapted processes for their fabrication and by their specific characteristics.
The physical requirements in relation to the substrate material are: production of narrowly delimited structures in a lateral direction ~e.g. by m~king use of a diffusion anisotropy during ion exchange), and/or a wavelength dependence (dispersion) of the refractive index increase n2 - nS necessary for wave guidance -~ I9503 930.0-51 X 9597 (in relation to the material surrounding the SOWCW) according to the following formula:

2 s > 0, where nS = nl, if nl > n3 or n~ = n3, if n3 > nl, d~
where n2 designates the surface refractive index of the waveguiding region.

The SOWCW is produced according to one of the following processes:
- ion exchange or ion indiffusion in dielectric crystals such as KTiOPO4 (KTP), LiNbO3, and LiTaO3, - ion exchange in glass, - injection molding, stamping or centrifugal processes with polyrners on suitable substrates such as Si, this will produce rib or inverted rib or Petermann waveguldes~
- SOWCW in lI-VI or III-V semiconductor materials, fabricated by epitaxial depositing processes on suitable substrates such as siO2, - SOWCW in II-VI or III-V semiconductor materials, fabricated by doping or alloying, - SOWCW in heterostructures of ternary or quaternary II-VI or III-V
semiconductor materials, - Rib or inverted rib or Petermann waveguides in II-VI or III-V semiconductor materials, - SOWCW in and on a suitable substrate material, preferably Si, by combining Si, sio2, SiON layers and/or other oxidic and/or nitride layers, - Sol-Gel processes on suitable substrate materials (S. Pelli, G. C. Righini, A.Verciani: ~Laser writing of optical waveguides in sol-gel fi/ms', SP~E2213, Intemational Symposium on lntegrated Optics, pp. 58-63, 1994), -- 21 ~721 3 19503930.0-51 X9597 - ion implantation in all above-mentioned materials.
The processes for manufacturing optical channel waveguides, in particular ion exchange and ion indiffusion in dielectric crystals, or ion exchange in glass, can be combined advantageously with the ion implantation process to obtain narrowly delimited structures.

To manufacture a wideband junction splitter according to this invention, a minimurn of three channel waveguides from which at least one is a SOWCW will be combined such that a combination, splitting, switching, deviation, or modulation of light becomes possible. This can be effected by using integrated-optical devices on the basis of two-mode interference such as Yjunction couplers, X-couplers, directional couplers, three-guide couplers, or BOA (in: U~Karthe, R. Muller, lnteg7ierte Optik ~Integrated Optics), Akademische Verlagsgesellschaft Geest & Portig K-G., Leipzig, 1991). Furthermore, integrated-optical or micro-optical reflectors (ll~illors, gratings, prisms) may be used for junction-splitting.
The minimum of one SOWCW of the wideband junction splitter is to be designed such that light from a wide wavelength range is guided in singlemode according to the formula ~w ~ 0.48 x ~ - 85 nm (where ~ and ~- are stated in nm), in particular light of discrete wavelengths or discrete narrow wavelength ranges from the entire visible spectrum.
The wideband junction splitter is dimensioned by its geometrical and optical parameters such that an efficient operation across a wide wavelength range, according to the formula ~v > 0.27 x ~ - 34 nm -- 2 1 ~ 7 2 1 3 19503 930.0-51 X 9597 (where ~ and ~, are stated in nm) is ensured. In relation to the wavelength ~ =
400 nm this means that, e.g., there is an efficient junction-splitting in a wavelength range ~v ' 75 mn.
Preferably, wideband junction splitters enable efficient junction-splitting of the light across the entire visible wavelength spectrum, in particular blue and red light simultaneously. With a junction-splittable bandwidth corresponding to the entire wavelength spectrum of visible light, there is a real white light junction splitter.
In integrated-optical devices based on two-mode interference, there is a second criterion in relation to determining the wideband characteristic vis-à-vis the SOWCW, which criterion will restrict the usable bandwidth. To ensure efficient operation, that is for example, a constant splitting ratio in splitting operation when the wavelength is varied, or a high extinction ratio in junction operation in integrated-optical interferometers, the oscillation build-up of the second lateral mode No2 is to be prevented in the widened coupling area.
The usable bandwidth ~N of the junction splitter will thus be determined, on theone hand, by the lesser value of the difference between the wavelength of the fundamental mode Noo oscillation build-up in the channel waveguide and the firstlateral or depth mode (Nol or Nlo) in the channel waveguide ~ ,), and on the other hand by the difference between the fundamental mode Noo oscillation build-up in the channel waveguide and the second lateral mode No2 in the widened coupling area (~v), that is by the lesser value of either ~v and ~, (Figure 6a).The wideband junction splitter according to the invention is advantageously usedfor combining light from a wide spectrum range, in particular from the entire visible light spectrum range, in a common SOWCW. In an advantageous further -- 2 1 8 7 2 1 3 19503 930.0-51 X 9597 application of the invention, all channel waveguides of the wideband junction splitter are SOWCW.
-If required, a coupling point may be actively influenced. To this end, the couplingpoint is designed as a controllable unit for the combination of beams and / or deviation of beams. If required, the wideband junction splitter comprises a modulation device for converting a suitable, generally electric, input signal into an optical amplitude or intensity signal, which allows separate active control of the light from two or more light sources or wavelengths up to very high control frequencies (into the GHz range, according to the current state of the art).

The amplitude or intensity-modulation of the light is implemented according to one of the followil1g principles:
- electro-optical light modulation by means of an integrated-optical interferometer structure, - acousto-optical light modulation by means of an integrated-optical intelrelometer structure, - thenno-optical light modulation by means of an integrated-optical intelferollleter structure, - magneto-optical light modulation by means of an integrated-optical intelrelometer structure, - opto-optical light modulation by means of an integrated-optical int~lrelollleter structure, - photo-thermal light modulation by means of an integrated-optical interferometer structure, -- ~1 8721 3 19503930.0-51 X9597 modification of the effective refractive index by injection or depletion of freecharge carriers in semiconductor materials, in connection with an integrated-optical interferometer structure, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical,or photo-thermal modulation using the Fabry-Perot effect, modulation by changing the effective refractive index by means of injection or depletion of free charge carriers in semiconductor materials, using the Fabry-Perot effect, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical,or photo-thermal cut-off modulation, cut-off modulation on the basis of the change in the effective refractive index as a result of the injection or depletion of the free charge carriers in semiconductor materials, controllable waveguide amplification, controllable polarization conversion in conjunction with a polarizing device or polarizing waveguide, waveguide mode conversion, electro-absorption modulation, modulation with the assistance of an integrated-optical switching or distributorelement, such as an X-coupler, three-guide coupler, directional coupler or BOA, modulation of the light source itself, or modulation by modifying the coupling efficiency between light source and waveguide.

- 21 8721 3 19503930.0-51X9597 At the coupling point, a spatial combination and/or splitting and/or deviation of light components and/or beam deflection is effected in the passive case, and, additionally, a modulation or switching of light components in the active case.

The wideband junction splitter can be operated so advantageously that light fromlight sources of different wavelengths may be injected consecutively into the relevant channel waveguide or SOWCW, and in the junction point, the light components are spatially combined, and in the common SOWCW the consecutive light components are modulated (time multiplex operation).

ln principle, all materials may be considered for use as substrate materials, inwhich it is possible to produce SOWCW meeting the above-mentioned requirements, and which, if necessary, provide an option for the conversion of amo~ul~ting input signal into a mo~ te-l optical amplitude- or intensity signal.

The invention refers to the use of a wideband junction splitter in devices requiring light of several wavelengths to be guided simultaneously within a usable wavelength range of several 100 nm in a SOWCW, and where a provision for controlling the amplitude or intensity of the light is required for the purposes of colour mixing, measurement technology, sensor technique, photometry, and spectroscopy, e.g. by lltili~ing interferometric measuring methods providing thebasis for a new multi-functional microsystem-technical device family.

The use of SOWCW in conjunction with modulation mech~ni~m~ provides thebasis for new integrated-optical detection and spectroscopy methods operating intelÇerollletrically (for example), and creates the possibility of using several wavelengths from a wide wavelength range simultaneously or consecutively in a -- 2 1 8 7 2 1 3 19503 930.0-5 l X 9597 SOWCW, and without such use being limited to just the visible spectrum of electromagnetic radiation.
The advantages of the invention consist of the possibility to manufacture devices and, for instance, electro-optical modules that can be produced by mass production means and allow mini~tllrization of their dimensions.
By means of the invention, it is possible to integrate on a mount, monolithically or in hybrid fashion, light sources, junction-splitting, and/or junction combination, control, and detectioll.

For analysis instrutnents, the integrated-optical implementation of the measurement setups favours a miniaturized design, in addition, the smallest sample quantities will be sufficient for analysis.
These smallest sample quantities may be used and still a very high measurement precision m~in~ined, as the interaction window must only be a fraction wider than the SOWCW and the length of the interaction window can be within the millimeter range.
By means of the measurement setups, all physical, biological, and chemical quantities of gases, liquids, and solids influencing the behaviour of the guidedlight or the behaviour of the channel waveguide itself can be measured, for instance by detecting any changes in absorption, refractive tndex, or diffusion in the SOWCW.
And for a given measurement setup, co~ il-g a wideband junction splitter, several wavelengths or at least one wavelength range can be freely selected froma wide wavelength spectrum.

The wideband junction splitter according to the invention offers the following advantages:

2 1 ~ 72 1 3 19503 930.0-51 X9597 singlemode wideband tr~n~mi~sion of light;
within the technical meaning, effective light modulation and/or switching capability into the GHz range (according to the current state of the art);
depending on requirements, it is possible to select a wavelength-dependent modulation device, or a modulation device independent of wavelength (e.g.
electro-absorption modulation, light source modulation, wedge filter);
low electro-optical modulation voltages (some volts) in comparison to volu1ne-optical Pockels or Kerr cells (some 100 volts), thus good combination possibilities with processes, structures, and devices in microelectronics;
when using KTiOPO4 (KTP) as a substrate material, high optical performance densities can be guided in the SOWCW without any interfering phase alterations, that is, there is a high resistance of the material against a light-induced alteration of the refractive index.

Brief Description of the Drawin~s Below, the invention will be described by means of figures. These show:
Figure 1: Principle of wideband junction splitter devices Figure 2: Illustration of the structure and the course of the refractive index in a Ti:LiNbO3 channel waveguide Figure 3: Bandwidth of the Ti:LiNbO3 junction splitter Figure 4: Illustration of the structure and the course of the refractive index in a Rb:KTP-SOWCW
Figure 5: Bandwidth of the Rb:KTP wideband junction splitter Figure 6: General illustration of the technically relevant wavelength range for efficient junction-splitting, as well as general illustration of the wavelength dependency of efficient Junctlon-spllttmg 2 1 8 7 2 1 3 19503 930.0-51 X 9597 Figure 7: Wideband junction splitter complete with modulation devicesigure 8: Wideband junction splitter complete with Mach-Zehnder interferometer modulatorsigure 9: Wideband junction splitter comprised of three-guide couplers with controllable light sourcesigure 10: Wideband junction splitter: design typesigure 11: Wideband junction splitter complete with controllable units for beam combination and/or beam deviation as a 2xl matrixigure 12: Wideband junction splitter complete with passive units for beam combination and/or beam deviation, and modulators, as a 3xl matrixigure 13: Wideband junction splitter complete with controllable units for beam combination andlor beam deviation as a mxn matrixigure 14: Photometer device with separate interaction celligure 15: Photometer device with interaction windowigure 16: Wideba nd junction splitter for time multiplex operationigure 17: Wideband junction splimer complete with phase modulators in the input branchesigure 18: Wavelength sensorigure 19: Wavelength-selective amplitude modulatorigure 20: Refractive index sensorigure 21: Wideband junction splitter complete with frequency converters for the spatial combination of light componentsigure 22: Wideband junction splitter for generating light components of differing wavelengths from the light of one wavelengthigure 23: Sensor for measuring length and refractive index changes - 2 1 8 72 1 3 19503 930.0-51 X9597 7. Wavs of Implementin~ the Invention Figure 1 shows the basic design types of a wideband junction splitter. The characteristics of a known titarlium-indiffused channel waveguide in LiNbO3, anda standard junction splitter based Ol1 such channel waveguides, are illustrated in Figure 2 and in Figure 3. This is contrasted with the characteristics of a singlemode integrated-optical wideband channel waveguide (SOWCW), according to this invention, and a wideband junction splitter according to this invention, which characteristics are illustrated in respect of their bandwidths,using a rubidium ~ potassium ion exchanged channel waveguide in KTiOPO4 (KTP), in Figure 4 and Figure 5.

In Figure 3, as well as in Figure 5, the illustration type selected is the effective refractive index Neff~ z of the mode in the channel waveguide, in relation to the valu~ of the refractive index of substrate nl as a function of wavelength ~. Each channel waveguide mode can be allocated an effective refractive index N.ff between the surface refractive index n2 and nl or n3 ~refractive index of the superstrate), whichever is the higher value.
The value of Neff depends on the wavelength, the substrate, the superstrate and waveguide refractive indices, or refractive index profiles, and the waveguide geometry. Each mode with index ik (i, k > 0, integer) will thus be illustrated in the diagrams by means of its effective refractive index as a line N~" where i symbolizes the order of the depth modes, and k the order of the lateral modes.
The channel waveguide is singlemode, if, for a given wavelength from a wavelength range, one and only one effective refractive index, namely the effective refractive index Noo of the fundamental mode, can be allocated.

`_ 2 1 872 1 3 19503 930.0-51 X 9597 For sufficient guiding of the light, from a technical point of view, the effective refractive index of the relevant mode must be at least S x 10-5 above nl and/or n3.
The bandwidth can thus be read off directly.
Figure 6a is a generalized description of the singlemode, and technically seen, efficiently guidable wavelength range in the chalmel waveguide as well as of thewavelength range of an efficient junction-splitting in a junction splitter.
Figure 6b shows the singlemode guidable wavelength range of the channel waveguide, as well as the wavelength range of the efficient junction-splitting, for SOWCW according to the invention in rubidium ~ potassium ion exchanged KTiOPO4 ~KTP), as well as for standard titaniurn-indiffused cllannel 2 1 ~ 72 1 3 19503 930.0-51 X 9597 waveguides in LiNbO3, respectively in direct depelldence of the wavelength itself.
In addition, in Figure 6b the area of the SOWCW al1d wideband junction splitter according to this invention will be delimited in general from current state-of-the-art channel waveguides and junction splitters.

Figure 1 first shows the basic design types of a wideband junction splitter.

Figure 1 shows singlemode integrated-optical wideband channel waveguides (hereina~er designated as SOWCW) 2, 3, and 5 embedded into a substrate material 1. The SOWCW 2 and 3 each have a respective input El and E2. At their outputs Al and A2, they are combined in a coupling point 6 and will be continuedas a combined SOWCW 5 to a common output AM.
According to Figure la, the coupling point is of the Y-type. The Y-type is not mandatory. Other devices for two-mode interference may be implemented such as three-guide couplers according to Figure lb, X-couplers according to Figure 1 c,directional couplers or BOA. If required, the coupling point 6 may be actively influenced.
To this end, the coupling point 6 is designed as a controllable unit for beam combination and/or beam deviation. All channel waveguides (SOWCW) 2, 3, and 5 in this example are of the same type and will guide the light across a large wavelength range, which is greater than 130 nm approximately (value given applies to short-wave visible light) in singlemode, in order to enable efficientjunction-splitting of light from a wavelength range greater than 95 nm approximately (see Figures 3, 5, and 6). The characteristic of the incoupling channel waveguides 2 and 3 to be SOWCW is not mandatory but always advantageous for any application. Light of wavelength~l or wavelength range Z1 S721 3 21 19503930.0-51X9597 ~1 will be applied at input E~ to the first SOWCW 2, and light of wavelength ~2 or wavelength range ~2 wi]l be applied at input E2 to the second SOWCW 3. At the common output AM of the SOWCW 5, spatially combined light is available, which is designated as mixed signal M. The wideband junction splitter can also be operated in the opposite direction, that is, in splitting direction, in order to split a light signal into light components which, if required, may be controlled individually in the SOWCW 2 and 3. According to Figure ld, the SOWCW are combined by means of integrated-optical reflectors R. The SOWCW 2 will be deflected via a 90 reflector Rl into the SOWCW 8. At the point where the SOWCW 3 and the SOWCW 8 meet, a second reflector R2 is located, which will spatially combine the light components in the SOWCW 2 and 3 and/or 8 (coupling point 6) and pass them on in the SOWCW 5. If required, the reflectors R may be designed as controllable reflectors.

Figures 2 and 3 provide initial descriptions using the example of a standard titanium-indiffused channel waveguide in LiNbO~.

Figure 2 shows a standard channel waveguide 17 in a substrate material 1.
To fabricate the standard channel waveguide, a titanium-indiffusion will be carried out in X-cut lithium niobate (LiNbO3) (X = crystallographic X-axis, corresponds to the y-axis in Figure 2) (R. ~ Schmidt, l.P. Kaminow, Appl. Phys.
Lett., Vol. 25 (19741 No. 8, pp. 458-460 ). To this end, a titanium strip 18 is sputtered onto the substrate surface.
At temperatures higher than 950C, the titanium will diffilse into the LiNbO3 crystal, by which the refractive index in the substrate material will be increased.
In lateral direction, the diffusion constant is approximately twice as large as in depth direction, that is why the titanium combination distribution in the crystal . - 2 ~ ~ 72 1 3 22 19503 930.0-51 X 9597 widens very considerably. Following the diffusion time period td, and for an initial strip width w, the refractive index profile created obtains a shape described bythe formulae below.
Titanium-indiffused chalmel waveguides in LiNbO3 are not capable of guiding light with a bandwith of several 100 nm in singlemode. The waveguide 17 is provided as a groove, not to any great extent geometrically delimited, with the width a and the depth t.

The groove has a refractive index distribution n~ f(x,y), with a surface refractive index n2=n~- (x''' = 0, y''' = 0), which is increased in relation to the refractive index nl of the surro~lnding substrate material. The diagrams in Figure 2 show the qualitative course of the refractive index in x direction and in y direction. The steady transition of the refractive index course in x direction (direction x" is actually shown here) and in y direction (direction y"' is actually shown here) is typical.

Figure 3 shows the wavelength range (bandwidth) of efficient junction-splitting by a Ti: LiNbO3 junction splitter as well as the wavelength range (bandwidth) oflight which is guided in singlemode in a titanium-indiffused channel waveguide in LiNbO3, as an example, and without restricting the general validity of the calculation for a referellce wavelength of 500 nm.
The graphs represent the effective refractive index for Z-polarized light (Nef~z, Z = c~ystallographic Z-axis, corresponds to x-axis in Figure 2) of the fim~ ental mode Noo and the first mode Nol in lateral direction for width a of the channel waveguide itself and the second mode No2 in lateral direction for the double width 2a of a channel waveguide, that is, corresponding to the increased width of the waveguiding area at the junction coupling point of a Y-splitter, BOA, or X-`~ 21 8721 3 23 19503 930.0-5 1 X 9597 coupler. A w = 3.0 ,~n wide, 15 nm thick sputtered titanium strip is used as a diffusion source, which widens in the junction coupling area to up to 2w (6.0 ~m). The diffusion temperature is 1000C, diffusion time will be 3 hours. The ratio of the titanium-ion diffusion constants in the LiNbO~ is DX/D~ ~ 2.
The depth profile is calculated as follows = n I + (ll2-lll) * exp (_(y~)2 / a~2)7 the lateral refractive index profile is calculated as follows n~, = n ~ + (n2-n~) * 0.5 [erf((2x'''+w) / 2a~) - erf ( (2x'''-w) / 2a~-)], where a~ = 2(D~td) 1/2, and corresponds to width a/2 in Figure 2, furthermore a! = 2(D!t~l) and corresponds to depth t in Figure 2 and amounts to 2 ,um. At ~=500 nm, nl=2.2492; n2-nl = 0.0080; the known wavelength dependence (dispersion) of the substrate index nl is less than zero. The wavelength dependence (dispersion) of (n2-nl) is known and also less than zero.
The value td represents diffusion time, erf the error function (cf. J. Ctyroky, M.
~ofi~an, J. Janta, J. Schrofel, "3-D Analysis of LiNb03: Ti Channel Waveguides and Directional Couplers" IEEE ~ of Quantum Electron.~ Vol.
QE-20 (1984), No. 4, pp. 400-409).
The channel waveguide described here guides in the wavelength range 490 nm to 620 nm - in a technically efficient sense - the fund~mental mode Noo only, i.e. the bandwidth of the channel waveguide will be ~" = 130 nm.
For efficient junction-splitting, it will be necessary to prevent the oscillation build-up of the second lateral mode No2 in the entire widened junction or splitter `~ 21 872l 3 19503930.0-51 X9597 area. For this reason, only the wavelength range between the oscillation build-up of fundamental mode Noo of the channel waveguide of width a (corresponds to original channel width w) at ~ = 620 nm and the oscillation build-up of the second lateral mode No2 in the junction splitter component widened to 2a ~corresponds to original channel width 2w) at ~ = 525 nm may be used. Thus the efficiently usable bandwidth ~N of the junction splitter reduces by 35 nm to thevalue ~v= 95 nm.
The effective refractive indices were calculated using the effective index method (G.B. Hocker, ~K Bums "Mode dispersion in diffused channel waveguides by theeffectiveindexmethod" Appl. Optics, Vol. 16(1977), No. l, pp. 113-118).

Figure 4 shows the singlemode integrated-optical wideband channel waveguide (SOWCW) 2, according to this invention, in substrate material 1: in this example, Z-cut potassium titanyl phosphate (KTiOPO4, KTP). (Z=crystallographic Z-axis, corresponds to the y-axis in Figure 4). (M. RoffschaL~, J.-P. Ruske, K Homig, A.Rasch, "Fabrication and Characterization of Singlemode Channel Waveguides and Modulators in KTiOPO4 for the Short Visible Wavelength Region', SPIE
2213, Intemational SymposizJm on Irltegrated Optics (1994) pp. 152-163).
The substrate material 1 will be provided with a mask leaving a gap open at the future channel waveguide location only. The ion exchange will be effected in a melt of rubidium nitrate complete with barium nitrate and potassium nitrate components. A diffusion is predomin~ntly effected in depth direction only, with the refractive index profile forn~ing which is described below. In a lateral direction, there follows a step profile of the refractive index. The fabrication of narrow structures, sharply delimited laterally, is ensured as the tr~n~mi~sion from the rrask into the waveguide occurs at the ratio of 1:1 due to almost complete lack of a side diffusion.

~ 2 1 8 7 2 1 3 25 1 9503 930.0-5 1 X 9597 The SOWCW 2 is provided as a groove, sharply delimited geometrically, with the width a and the depth t. The groove has a refractive index distribution nw-f(x,y), with a surface refractive index n2=n~. (-a ~ x" < 0, y" = 0), which is increased in relation to the refractive index nl of the surrounding substrate material.
The diagrams in Figure 4 show the qualitative course of the refractive index in x-direction and in y-direction. The steep jump of the refractive index course in x-direction (direction x'' is actually shown here), and the comparatively high increase of the refractive index from nl to n2 in y-direction (direction y' is actually shown here), are typical.

Figure 5 shows the wavelength range (bandwidth) of efficient junction-splitting by a Rb:KTP junction splitter as well as the wavelength range (bandwidth) of light which is guided singlemode in a rubidium ~ potassium ion-exchanged channel waveguide in KTP, as an example, and without restricting the general validity of the calculation for a referellce wavelength of 500 nm.
The graphs represent the effective refractive index for Z-polarized light (Neff~ z, Z = crystallographic Z-axis, corresponds to y-axis in Figure 4) of the fundamental mode Noo and the first mode Nol in lateral direction for width a of the channel waveguide itself and the second mode No2 in lateral direction for the double width (2a) of a channel waveguide, that is, corresponding to the increased width of the waveguiding area at the junction coupling point of a Y-splitter, X- coupler, or BOA. At ~ = 500 nm, nl= 1.9010; the known wavelength dependence (dispersion) of the substrate index nl is less than zero ~described in: L.P. ShiApplication of crystals of the KTiOPO4 -type in the field of integrated optics, Dissertation Univ. Cologne (1992)) .
Furthermore, n2-n, = 0.0037 = const. applies to the entire wavelength range.

-- 21 8721 3 26 19503930.0-Sl X9597 For the diffusion constants, the following holds Dy/D~ ~ 10-3.
The lateral refractive index profile is thus a step profile (cf. Figure 4) with the width a = 4.0 ~lm, or 2a (8.0 ,um) for the m~ximum width in the junction area.
The depth profile is calculated as follows n~, = n I + (n2-nl) * erfc (-y''/t) where t = 4.0 ~n, erfc = complementary error function. The SOWCW described in this example guides - in a technically efficient sense, and within the range 470 nm to 870 nm, - the fimdamental mode Noo only, that is, the bandwidth of the channel waveguide is ~ = 400 nm.
For efficient junction-splitting, it will be necessary to prevent the oscillation build-up of the second lateral mode No2 in the widened junction or splitter area.
For this reason, only the wavelength range between the oscillation build-up of fundamental mode Noo of the channel waveguide of width a at ~ = 870 nm and the oscillation build-up of the second lateral mode No2 in the junction splittercomponent widened to 2a at ~ = 485 nm may be used. Thus the efficiently usable bandwidth ~N of the junction splitter according to the invention reduces slightly by 15 nm to the value ~,.= 385 nm.
The effective refractive indices were calculated using the effective index method.

Figure 6a shows a general illustration of the technically relevant usable wavelength range for singlemode waveguiding in a channel waveguide, and for efficient junction-splitting in a junction splitter. In connection with this Figure, technically relevant signifies that the effective refractive index Neff must be at least S x 10-5 above ns, where nS ~lesi~tes the value of substrate index nl or superstrate index n3, whichever is the greater, to ensure a sufficiently low waveguide attenuation, e.g. 1 dB/cm.

2 1 8 72 1 3 19503 930.0-51 X9597 To each given wavelength in the range A~, one and only one effective refractive index, i.e. the effective refractive index of fundamental mode Noo will be allocated.
The singlemode range of the channel waveguide will be deterrnined by the efficient oscillation build-up, from a technical point of view, of fundamental mode N"o at wavelength ;~a+~ V on the one hand, and by the efficient oscillation build-up, from a technical point of view, of the first mode in lateral direction Nol or of the first mode in depth direction Nlo at wavelength ~a on the other hand. For efficient junction-splitting, it is necessary to prevent the oscillation build-up of the second lateral mode No2 in the widened junction- or splitter area, that is the coupling area with increased, e.g. doubled, waveguide width.
This leads to a further criterion which restricts the usable bandwidth of the junction splitter when compared against the bandwidth of the channel waveguide, namely the spectrum width ~v, that is the wavelength range between the oscillation build-up of the fundamental mode Noo of the channel waveguide with asingle width, at ~a + ~;~W~ and the oscillation build-up of the second lateral mode No2 in the widened coupling area, e.g. doubled width, at wavelength~b.
For this reason, the usable bandwidth ~N for efficient junction-splitting is thelesser of the two values ~ or ~v.

Figure 6b shows the singlemode tr~n~mi~sible wavelength ranges of the channel waveguide according to the current state of the art (consisting of ~
indiffused LiNbO3, Ti:LiNbO3) and the SOWCW according to this invention (con~isting of rubidium~potassium ion-exchanged KTiOPO4, Rb:KTP) as well as the wavelength ranges for efficient junction-splitting of the junction splitter according to the state of the art and the wideband junction splitter according to the invention, respectively as a function of wavelength ~.

~ 2 1 ~ 72 ~ 3 28 19503 930.0-51 X 9597 From the minimum of three channel waveguides forming the wideband junction splitter, at least that cllannel waveguide which, according to the application is to transmit a wide wavelength spectrum, must be a SOWCW.
The calculation of the effective refractive indices, upon which the determination of the singlemode tr~n~mi~sible wavelength ranges is based, was done by means of the effective index method.
Based on the known wavelength dependence (dispersion) of the refractive index increase required for wave guidance, as we~l as on the wavelength dependence ~dispersion) of the substrate index, and starting from the concrete reference wavelength ~a, first the waveguide depth, then the waveguide width (until respective oscillation build-up of the first mode) and finally the wavelength ~until fundamental mode had disappeared), were varied in this calculation.
The upper limit of the singlemode tr~n.cmi~.sible wavelength range ~ will be thewavelength ~a+~v where the effective refractive index Noo of the fundamental mode for the channel waveguide is sx1~5 above the substrate index.
In Figure 6b, the singlemode tr~n~mi~sible wavelength range of a SOWCW
according to the invention is situated above the straight line with the equation ~. = 0.48 x ~ - 85 nm (where ~ and ~w are to be stated in nm).
For efficient junction-splitting, it is necessary to prevent the oscillation build-up of the second lateral mode No2 in the entire widened junction- or splitter area.For this reason, only the wavelength range between the oscillation build-up of fundamental mode Noo of the channel waveguide of width a at wavelength ~a + ~h and the oscillation build-up of the second lateral mode No2 in the junction splitter component widened to 2a at wavelength ~b may be used.

-- 2 1 ~ 7 2 1 3 29 19503 930.0-51 X 9597 In addition to the graphs representing the bandwidths of channel waveguides A~
the graphs describing the bandwidths of junction splitters A~v are also shown.
From the state of the art, it can be deduced that the size of the area for efficient junction-splitting ~v must meet the inequation ~v ~ 0.27 x ~ - 34 nm (where ~ and ~ are stated in nm~, in order to characterize a wideband junction splitter. The region corresponding to a wideband junction splitter has been marked in grey in Figure 6b. In principle, the area for efficient junction-splitting is restricted by the lower limit (;~nin) as well as the upper limit (~na~) of the optical tr~n~mi~sion area of the waveguide material (see Figure 6a).
Using other suitable waveguide materials, these two inequations can also be applied to wavelengths less or greater than for ~qnin or ~ma~ of the substrate material KTiOPO~ (KTP), here calculated and described by way of example.

The Figures 7 to 10 show first implementation examples of wideband junction splitters.

In the example shown in Figure 7, light from three light sources of dilreling wavelengths ~ 2, and ~3, is injected into respectively one each of the three SOWCW 2, 3, and 4, combined at the coupling points 6, and spatially combined in SOWCW 8 or SOWCW 5, passed on, and made available at output AM of the SOWCW 5 as mixed signal M.
To control the amplitude or intensity of the light components in the individual SOWCW, the light from each light source may be selectively modulated. In this example, this is effected by means of the signals Sl, S2, and S3, which are applied to controllable amplitude or intensity modulators AMI, AM2, and AM3. The controllable amplitude modulators or intensity modulators AMI, AM2, and AM3 2 1 8 7 2 1 3 19503 930.0-51 X 9597 are located in the various individual SOWCW 2, 3, and 4. Depending on the control signals, the modulated intensities of the various wavelengths will result in a mixed signal M comprised of the spatially superimposed light components whose respective intensities can be adjusted by means of the amplitude modulators for the individual wavelengths. In the wavelength range for visible light, the mixed signal M can be perceived as a subjective colour impression.
Due to the possibility of electro-optical modulation into the GHz range (currentstate of the art), the device can be utilized for generating fast ch~n~ing lightintensities, and, by means of the spatial combination of light, for fast ch~n~ngphysiological mixing of colours in the human eye.

Figure 8 shows an implementation of a wideband junction splitter in a KTiOPO4 (KTP) substrate 1 with amplitude modulators or intensity modulators, designed asMach-Zehnder interferometer modulators MZI" MZI2, and MZI3 .
By applying the control voltages Ul, U2, and U3 to the electrodes, the propagation constant of the light in the two branches of a Mach-Zehnder illlel~elometer willbe changed to different values via the linear electro-optical effect in the electro-optically active material. In place of the combination in the intelrerollleter, there will either be a constructive or destructive intclr~l~nce, depending on the phasing of the light components. These control voltages thus govern the amplitude of thelight components in the SOWCW 2, 3, and 4 (see also Figure 18).

According to Figure 9, there is a further option for amplitude or intensity modulation consisting of the modulation of the light sources Ll~ L2, and L3, which is effected by means of the control signals Sl, S2, and S3, e.g. via the diode current for laser diodes.

1 9503 930.0-5 1 X 9597 - 21 ~721 3 31 Further amplitude modulators will then not be mandatory on the SOWCW. The wideband junction splitter features coupling points 6 which are here designed asthree-guide couplers.

Figure 10 illustrates wideband junction splitters whose coupling points 6 or 6' effect more than a two-times split or more than a two-times combination. The solutions described in the above Figures may also be applied to wideband junction splitters the coupling points of which feature more than 2 inputs or outputs. In splitting direction, the light will not necessarily split into equal light components.
Figure lOa and Figure lOb show a wideband junction splitter in which the input SOWCW will be split, at coupling point 6', in the form of a Yjunction splitter into three SOWCW 2', 3', and 4', or in which three SOWCW 2, 3, 4 will be combined, at coupling point 6, in the forrn of a Yjunction combiner.
Figure lOc and Figure lOd show a triple wideband junction splitter, whose coupling point is made up of three-guide couplers, in splitting or combining operation.
Figure lOe and Figure lOf show a triple wideband junction splitter, whose coupling point is made up of integrated-optical reflectors, in splitting or combining operation.
In principle, it is possible to combine or split any number of waveguides at a coupling point 6 (Figure lOg and Figure lOh). However, limits are set by the technological mastery of the manufacturing processes and the engineering design of the coupling point. In splitting operation of the wideband junction splitter, the light of wavelength ~O or wavelength range Q~ will be divided up into each SOWCW. In each SOWCW, there is coherent light, provided that the injected light is coherent. In junction operation, the light components of the same or - 2 1 8 7 2 1 3 32 19503 930.0-Sl X 9597 differing wavelength are spatially combined. The light components do not interfere with each other. Figures 11 to 1 3 show further integrated-optical implementation variants of the wideband junction splitter, in which the couplingpoints 6 are generated by waveguide intersections.
The intersection points act, depending on the requirement, as completely passiveintersection points, or they are coupling points 6 for the spatial combination of light components, or they are designed as controllable units for the spatial combination of beams and/or deviation of beams 7, that is as elements capable ofswitching, mod~ ting, or deviating, and spatially combining light. The controllable units for the spatial combination of beams and/or deflection of beams 7 operate on the basis of the two-mode interference as X-couplers, directional couplers, or BOA.

Figure 11 shows the intersection of two SOWCW 2 and 3 with a further SOWCW 5 as a 2xl matrix. The intersections (coupling points 6) are formed as the controllable units for spatial beam combination and/or beam deviation 7' and7''. Light of two wavelengths ~1 and ~2 iS injected into one each of the SOWCW
2 and 3. The active coupling points act as selective light gates, which allow the light in the common SOWCW 5 to pass in the direction of the mixed signal M
completely uninfluenced, but deflect the light components of the wavelengths ~1 and ~2 in the SOWCW 2 and 3 as a function of the applied control signals Sl and S2 with di~.illg electro-optical intensity in the direction of the SOWCW 5, withthe light components in the SOWCW 5 being spatially combined and available as mixed signal M at output AM. The guided light components that are not completely deviated are passed forward in the SOWCW 2 and 3 to the blind outputs B.

-- 2 1 8 72 ~ 3 33 19503 930.0-S1 X 9597 Each controllable unit for beam combination and/or beam deviation 7' and 7'' is dimensioned such that it acts for the selected wavelength ~ or ~2, respectively, as a modulator, and simultaneously deflects the light component~ and spatially comb;ning this component with the other light component. The respective other wavelength is not, or only slightly, influenced by the modulator.
In respect of a rem~ining mutual interaction of the controllable units for spatial beam combination andlor beam deviation 7' and 7", the degree of this mutual interaction is compensated by an active control of the control signals and/or light sou~ces.
This device can be advantageously operated in time-multiplexed fashion so that the problems with decoupling of the controllable units for spatial beam combination andlor beam deviation 7' and 7" do not occur. Due to the possible very high control frequency, this can be implemented easily.
Furthermore, a third light component of the wavelength ~3 may be injected into an input E3 of the SOWCW 5. This light component may be spatially combined with the iight components injected into the SOWCW 2 and 3.

Figure 12 shows a further integrated-optical implementation variant of the wideband junction splitter as a 3xl matrix. The SOWCW 2, 3, and 4 intersect a further SOWCW 5. The intersections are passive coupling points 6, which spatially combine light components in the SOWCW 5. The modulators AMl, AM2, and AM3 are located on each of the SOWCW 2, 3, and 4 in order to modulate the light components. Light from three wavelengths ~ 2, and ~3 is respectively injected into one each of the SOWCW 2, 3, and 4. The coupling points 6 act as light beam combiners and light beam deflectors. The spatially combined light is fed out from the SOWCW 5 as a mixed signal M. At the SOWCW 2, 3, and 4, electro-optical modulators AMI, AM2, and AM3 are - 21~37213 34 located which allow the light compollents of wavelengths ~ 2, and ~3 to pass with di~eril~g intensities, as a fiu1ction of the applied control signals S ~, S2, and S3 Furthermore, here also a light component of wavelength ~ may be injected into an input E~ of the SOWCW S. Tl~is light component may be spatially combined with the light components guided in the SOWCW 2, 3, and 4.
Altematively, for the case of three light components being utilized, one of the SOWCW 2, 3, or 4, complete with its associated modulators and coupling points may be omitted.

Figure 13 shows a further integrated-optical implementation variant of the wideband junction splitter as a 3x4 matrix. The intersections are either points which transmit light into the SOWCW in completely uninfluenced fashion (passive intersecting point), or passive coupling points 6 or controllable units for the spatial combination of beams andlor deviation of beams 7.
The light from three wavelengths ~ 2, and ~3, iS respectively injected into one each of the SOWCW 2, 3, and 4. The SOWCW 2, 3, and 4 intersect the four SOWCW 8', 8'', 8''', and 5.
To elucidate their function, the intersecting points are shown in the form of a matrix. At the intersecting points determined by the column-lines l-l, 2-2, and 3-3, actively controllable units for the spatial combination of beams and/or deviation of beams 7 are located. These units serve to modulate the three light components.

In the column-lines 1-4, 2-4, and 3-4, passive coupling points 6 are located, which sp~ti~lly combine and/or deflect the light components. The coupling points6 will not be controlled here. They are used for spatially combining the light 19503 930.0-5 1 X 9597 21~7213 35 components into the mixed signal M in the common SOWCW 5. Any light components which are not required will be guided to the blind outputs B of the SOWCW2,3,4,8',8",and8"'.
Furthermore, here also additional light components may be injected into the inputs E4, E5, and E6 of the SOWCW 8', 8'', and 8"', and are controllable.
These light components may be spatially combined with the light components guided in the SOWCW 2, 3, and 4.
The Figures 14 and 15 show devices for determining the concentration of a given substance by photometric measurement. The integrated-optical implementation of the measurement setup, by means of wideband junction splitters, enables rniniaturization of the sample quantity and a simultaneous increase in the bandwidth usable for the measurement, as compared to standard solutions.

21 872 1 3 19503930.0-51 X9597 In Figure 147 the absorption of a medium to be measured 16 ~liquids or gases) contained in a separate interaction cell 14 is determined by a photodetector 12.
These tr~n~mi~sion measurements can also be carried out on a solid substance (not shown here). In addition, reflection measurements can be carried out (not shown here).
Light of three different wavelengths is respectively injected into one each of the SOWCW 2, 3, and 4, spatially combined, and then radiated through an interaction cell 14 located between output AM of the common SOWCW S and the photodetector 12, in which interaction cell 14 there is a liquid 16 to be measured.
Advantageously, there is a feed-out device 11 between the interaction cell 14 and the waveguide output AM for feeding out light and beam shaping. The measurement can be carried out according to one of the procedures described below:
a) There is a time-multiplexed feed-out of the individual light components at waveguide output AM The absorption is measured directly (i.e. without filter) for the respective wavelength.
By means of the modulators AMl, AM2, and AM3 in each SOWCW 2, 3, and 4, ligllt components may be switched by control sign~l~ S1, S2, and S3, or a switching of the light sources themselves is effected.
For a fluorescence measurement, filters Fi are advantageously located between the interaction cell 14 and the photodetector 12 in order to separate excitationlight and measurement light.
b) There is a simlllt~neous injection of all light components into the respective inputs of the SOWCW and a simultaneous feed-out of the light components at the output of SOWCW AM. The measurement wavelength is selected by swivelling a filter Fi between interaction cell 14 and photodetector 12 (without modulators).An amplitude modulation of the light components is as such advantageous for all 2 1 8 7 2 1 3 37 19503 930.0-5 l X 9597 measurements, as higher degrees of measurement accuracy may usually be achieved by means of dynamic measurement procedures.
The number of wavelengths used is not restricted to three; this number may be two or more, depending on the relevant purpose.

According to Figure 15 the absorbing effect of media to be measured 16 ~gaseous, liquid, solid) on the evanescent field (located in the superstrate) of the guided wave is measured and evaluated.
To this end, the covered common SOWCW 5 will be provided with a defirled interaction window 15, onto which the medium to be measured 16 is applied.
The light components of th~ wavelengths ~ 2, ~3 are modulated by means of the amplitude modulators AMI, AM2, and AM3.
By absorption of the medium to be measured itself or by a change in the surface scattering, a change in waveguide attenuation is caused, which is expressed as achange in the photo current Iph . This variant utilizes the fact that, with light of a mode guided in the channel waveguide, a part of the electric or magnetic field will be guided outside the SOWCW itself (evanescent field). These field components may thus be accessed and influenced from outside the SOWCW. If an absorbing medium is on the SOWCW, then the evanescent field itself -depen~ling on absorption - will be attenuated, or the surface scattering of the SOWCW will be changed by applying a medium which need not necessarily be absorbing. Both will cause the waveguide ~ttenu~tion to change, and this can be measured by means of the photodetector 12.
The surface of the substrate which comes into contact with the medium to be measured, will be covered by a buffer layer (e.g. SiO2) excepting only the interaction window 15. In this way, the evanescent field will be accessible only in the interaction window area. Also, a precisely defined measurement length will be 2 1 8 7 2 1 3 38 19503 930.0-51 X 9597 defined in this way (as the total absorption depends on the length of the interaction window).
-Using this measurement setup, it is possible to measure e.g. the absorption,refractive index, or scattering, and thus determine the influence of those physical,biological, and chemical quantities ~to be rneasured) of gases, liquids, and solids, which cause a change in the behaviour of the guided light or the chalmel waveguide as such.

A further implementation variant is that the interaction window 15 is coated with a substance reacting to physical, chemical, or biological external influences, which substance, when acted upon by such external influences, will influence thebehaviour of the guided light or the SOWCW as such.
The integrated-optical implementation of the measurement setup favors a miniaturized structure. The smallest sample quantities can be used, as the interaction window must only be just a fraction wider than the waveguide, and the length of the interaction window can be within the millimeter range.

Figure 16 shows a wideband junction splitter which is operated in time-multiplexed fashion. At the inputs El and E2, ~ l.c of constant amplitude are alternately applied and will be amplitude-modulated following the spatial combination of the light components as a function of the signal S applied to theamplitude modulator AMI. Diagram a) shows the amplitude curve of the applied time-multiplexed signal S of wavelengths ~1 and ~2 -Diagram b) shows the curve of the signal S for mo~ ting the light components.
Diagram c) shows the curve of the combined light components (mixed signal M)available at output AM

_ 19503 930.0-51 X 9597 2187213 39 Figure 17 shows a wideband junction splitter according to this invention, with at least one SOWCW 2 and/or 3 being provided with an electrode structure 10 for phase modulation.
The electrodes 10 have an effective electrode length L r~nging from some millimeters to some centimeters, as well as an electrode gap d of some,um.
The requirement for a light modulation capability is met by the use of a substrate material which allows a possibility for influencing the phase of an optical modeguided in a channel waveguide.
In the example, KTiOPO~ (KTP) is used as a substrate material. The input signal is a discrete wavelength ~ or a wavelength range A~.
Figure 17a shows a wideband junction splitter whose SOWCW 2 is provided with electrodes 10 for phase modulation.
When the same wavelength ~l is applied to inputs El and E2, and if coherent light is used, there will be either constructive or destructive intelrerellce at coupling point 6, depending on the actual phasing. Here, the effective electrode length in the individual waveguide 2 is L.
Figure 1 7b shows a wideband junction splitter whose two SOWCW 2 and 3 are respectively provided with electrodes 10 for phase modulation operating by push-pull. When the same wavelength ~l is applied to inputs El and E2, and if coherent light is used, there will be either constructive or destructive interrerence at coupling point 6, depending on the actual ph~sing. Here, the effective electrodelength in each individual waveguide 2 or 3 is L/2. If ~l is applied to the inputs El and E2, the entire effective electrode length is L, as the electrodes in the example are of length L/2, but operate in push-pull fashion, thus c~llsin~ the lengths to be added up. Phasing may be controlled by the modulation voltage U. Using SOWCW ensures functional operation across a wide wavelength band.

~ 2 1 ~ 7 2 1 3 40 1 9503 93{).0-S 1 X 9597 To provide the light capable of interference, which is required at the coupling point 6 in Figure 1 7a or 1 7b, a wideband junction splitter may be used in splitting direction (Figure 1 7c).
Light of a wavelength ~ or a wavelength range ~ is applied to an input E of a SOWCW 5'. The SOWCW S' is split into the SOWCW 2 and 3 at coupling point

6'. Each SOWCW 2 and 3 will then guide light capable of inte-rerellce. Figure 17c thus represents a Mach-Zehnder interferometer (MZI) modulator made up of SOWCW.
This wideband modulator operates wavelength-selectively.

Figure 18 shows the wideband junction splitter from Figure 17c with the provision of interference-capable light by means of a wideband junction splitter in splitting direction. This creates a MZI structure made up of SOWCW which due to its wide bandwidth is used as a wavelength sensor.
Light of the wavelength ~ to be determined is injected into input E of the SOWCW 5', which is followed by the integrated-optical MZI structure. Both branches are provided with phase modulators operating in push-pull fashion (electrodes 10). This enables phase modulation of the light components guided inthe intelrerollleter arms. If a voltage U applied to the electrodes 10 is changed, the electro-optical effect will cause the phase of the light guided in the i.llel rerollleter arms to be changed, too, and thus there will also be a change in the amplitude or intensity of the light fed out at output A.
The modulated light will be detected by a measurement device 9.

In this example, the light will fall onto a photodetector 12 by means of which the guided light tr~n~mi~sion performance will be determined. The measurement l9503 930 0-51 X 9597 setup consists of a feed-out device 11, which bundles the modulated light onto photodetector 12.
A display unit 13 indicates the light tr~ mi~sion perforrnance measured by the photodetector 12.
The correlation between the electrical modulation voltage and the phase of the guided optical mode in the case of an electro-optical modulator in Z-cut KTP andat TM light (that is, the normal to surface of the substrate, and the direction of the electric field vector of the linearly pola~ized guided li~ht, correspond to the crystallographic Z axis) are determined by:

U = - (~ d) / (~ L llz3 r~3 r) (1).
The half-wave voltage U,~ thus corresponds to a phase shift of ~, according to U,~ d) / ~L nz3 r33 r) (2) If a ramp voltage (Figure 18, left-hand diagram) is applied to the electrodes, the photocurrent changes according to the guided light tr~n~mission performance at the modulator output (Figure 18, right-hand diagram).
From this, U" (voltage between a minimum of guided light tr~nsmi~sion performance and an adjacent maximum) or a multiple of ~, may be determined.
According to (2), U,~ is dependent on the wavelength. Using a calibration curve U"= f(~), determined during sensor production, the wavelength of the light may be determined by means of measuring the half-wave voltage.
The photocell must ensure - here, in connection with the use of the wideband junction splitter according to the invention - the detectability across the entire wavelength range.
The light source must not emit any wideband light as the line width determines the resolution of the measurement setup, that is, if the resolution is to be fully 1 9503 930.0-5 1 X 9597 exploited, line width must be within or below the resolution order of magnitude.Instead of the Mach-Zehnder interferometer structure, integrated-optical interferometer structures, e.g. Michelson interferometer, may also be used. The basic operating principle is analog.

Figure 19 shows a wideband optical filter which filters out some light componentfrom a wavelength range ~E. This is effected by means of the wavelength selectivity of the Mach-Zehnder interferometer structure used in the example. The wavelength range ~A, decoupled at the output, contains the rem~ining part of thewavelength range ~;~E.
If the wavelength range ~E iS white light, the decoupled wavelength range ~i~A
corresponds to the complementary colour of the light component filtered-out.

-~ 2187213 43 19503930.0-51X9597 Figure 20 shows a miniaturized sensor for spectral determination of refractive indices, which sensor can be operated in wideband fashion. Light of differing wavelengths is spatially combined by means of a wideband junction splitter and then guided through a Mach-Zehnder interferometer structure. The amplitude or intensity modulators AMi are used to select the required wavelength. One arm of the Mach-Zehnder interferometer MZI is provided with an interaction window 15, similar to Figure 15; the amount of phase shift when applying the medium to be measured is determined according to the length of this interaction window; the other branch can be provided with a phase modulator in order to increase measurement precision and to determine the direction of the refractive index difference between the superstrate without andlor with the medium to be measured 16.
When applying the medium to be measured 16, the propagation constant of the guided wave is changed due to the changed refractive index of the superstrate;
this causes a change in phase, which can be determined interferometrically. The interferometer converts this change in phase into an amplitude signal or intensity signal. From the refractive index di~erellces, it is possible to determine substances or their concentration. The number of inputs is delellnilled by the number of di~erelll wavelengths of fixed coupled light sources. If a light source is used which is capable of providing selectively the light of several wavelengths,only one input will be required.

Figure 21 and Figure 22 show devices with SOWCW, which are suitable for generating and sp~h~lly combining light components of difre~ g wavelengths.
If laser diodes need to be used as light sources, the provision of the blue and green lights in this format is cullel~lly not yet possible. To this end, the principle for generating the second harmonic may be applied, if non-linear optically active l 9503 930.0-5 1 X 9597 21 ~721 3 44 materials are used (e.g KTP~. Between pumping wave and the second harmonic, phase-matching must be achieved. In KTP, the principle of quasi-phase-matching (QPM) is used.
To this end a piece of the waveguide is segmented in order to cause a ferro-electric domain inversion. In this way, phase-matching between pumping lightwave and harmonic lightwave is achieved. Pumping light of sufficient power is then capable of generating light of half the wavelength that is, e.g., the laser diode light with a wavelength of 830 nm is transformed into light with a wavelength of 415 nm. Further higher harmonics can be generated, e.g. light of wavelength ~/4.

A further variant for frequency conversion is the sum frequency generation (SFG)or difference frequency generation. Both variants can be carried out in KTP (e.g.
M.L. Sundhein1er, A. Villeneuve, G.~ Stegemann, and ~D. Bierlein, "Simulfaneous generation of red, green and blue li~ht in a segmented KTP
waveguide using as single source', Elecfronics letfers, 9th June 1994, vol. 30, No. 12, pp. 975-976) . By means of both variants, it is possible for instance toconvert infrared light into visible light of different discrete wavelengths.

According to Figure 21, devices for frequency conversion F~J are respectively fitted to one each of the SOWCW 3 and 4. The wavelength ~2 will be transformed into wavelength ~4, and the wavelength ~3 wili be transformed into wavelength i~5. The wavelengths ~ 4, and ~5 are provided as spatially combined light at mixed signal output AM. Which and how many SOWCW will be fitted with frequency conversion devices FU, will depend on the relevant use of the wideband junction splitter.

-- 1 9503 930.0-5 1 X 9597 21~7213 45 According to Figure 22, light of wavelength ~, enters into wideband junction splitters operating in splitting mode. Light components of wavelength ~" enter into the SOWCW 2', 3', and 4'. In each of the SOWCW 2', 3', and 4', a frequency conversion device FU is located.
Each frequency conversion device FU respectively generates the wavelength ~1, ~2, and ~3- In Figure 22a, the light components of wavelengths ~ 2, and ~3 may be decoupled. In Figure 22b, these light components are spahally combined in thefollowing wideband junction splitters in junction mode.
Spatially combined light of wavelengths ~ 2, and ~ is provided at output AM.

Figure 23 shows integrated-optical sensors for measuring any changes in the length and/or refractive index values.
The sensors are implemented by means of an integrated-optical Michelson interferometer structure using SOWCW as waveguides.
Figure 23a uses two single wideband Yjunction splitters.
Figure 23b uses a directional coupler, and Figure 23c uses an X-coupler or a BOA.
The operating principle of the sensor for measuring length changes is the same in all the examples. Light of a wavelength ~1 is injected into input E of the SOWCW2'. At coupling point 6' (Figure 23a) or at coupling point 6 (Figures 23b and 23c), the light is divided into two waveguide arms and decoupled at the detector outputs Dl and D2. By means of the decoupling device 11, this light is directed onto two mil~ols. One mirror Sp(f~ is in a fixed position. In place of this mirror, it is also possible to apply a reflecting coating to a waveguide end surface, or anintegrated-optical reflector in the SOWCW can be positioned ahead of the waveguide output. The second mirror Sp(b) is mounted on the movable object to be measured.

1 9503 930.0-5 1 X 9597 By means of the 1nirrors, the light components are reflected back into waveguideoutputs D] and D2, and brought to interference on their second path through the waveguide structure in coupling poirt 6' (Figure 23a) or in coupling point 6 (Figure 23b and 23c).
The superimposed light is divided again and may be decoupled at output A as well as at input E. The light which may be decoupled at output A is directed onto a photodetector 12, in which a photocurrent ~ph iS generated.
If the optical path length in the decoupling branch between D2 and Sp(b) is now changed, the phasing between the two reflected and recoupled light components also changes, and thus also the arnplitude or intensity of the signal applied to the photodetector. A change in position of ~/2 of the mirror Sp(b) in beam directioncorresponds to a full modulation of the photocurrent l~h.
For an additional use of a phase modulator in the waveguide branches, provided for in Figures 23a to c, and implemented in this example by the electrodes 10 applied to the SOWCW, and/ or simultaneous injection of the light of two wavelengths ~1 and ~2 in the SOWCW 2' and wavelength-selective measurement, a direction detection in respect of the phase change is provided.

By using SOWCW, it is furthermore possible to implement an increase in resolution capability by means of the option for using shorter wavelengths.
Cullelllly, no channel waveguide is known, in which light from the wavelength area of the blue light or even shorter wavelengths can be guided and modulated in singlemode.
If mirror Sp(b) is fixed and a measurement medium is inserted between the mirrorSp(b) and detector output D2~ then this represents a sensor for determinin~ the refractive index of the measurement medium.

19503 930.0-5 1 X 9597 21~7213 47 Reference Symbols 1. Substrate 2. SOWCW or challnel waveguides 3. SOWCW or channel waveguides 4. SOWCW or channel waveguides 5. Common SOWCW.
6. Coupling point

7. Controllable unit for the spatial combination of beams and/or beam deviation

8. SOWCW or channel waveguides

9. Measurement device 1 0. Electrodes I l. Decoupling device (outcoupling device) 12. Photodetector 13. Display urit 14. Interaction cell 15. Interaction window 16. Medium to be measured 17. Titanium indiffused channel waveguide in LiNbO~
18. Titanium strip Ll, L2, L3 Light sources MZII, MZI2 MZI3 Mach-Zehnder interferometer AMI, AM2, AM3, AM4 Amplitude modulators E, E" E2, E3 Light inputs A, Al, A2, A3 Light outputs 2 1 8 7 2 1 3 48 19503 930.0-51 X 9597 Sl, S2, S3 Control signals U" U2, U3 Control voltages R, Rl, R2 Integrated-optical or micro-optical reflectors M Mixed signal AM Mixed signal output U Electrode voltage Iph Photocurrent p Electro-optically generated change in phase d Electrode gap L Overall electrode length nz Refractive index for Z-polarized light r33 Component of the linear electrooptical tensor rk connecting the external electrical field in Z-direction with the refractive index for Z-polarized light r Overlap factor between the external electrical field of the electrodes and the internal electrical field of the guided optical mode T Time interval tM Measuring time (axis) ST Wavelength selective beam-splitter Sp(fl Fixed mirror Sp(b) Movable mirror Dl, D2 Channel waveguide outputs for detection D~, D~, Dz Diffusion constants Noo Effective refractive index of the fundamental mode of the charmel waveguide 19503 930.0-S1 X 959~

N", Effective refractive index of the first mode in lateral direction of the channel waveguide Nlo Effective refractive index of the first mode in depth direction of the channel waveguide No2 Effective refractive index of the second mode in lateral direction of the channel waveguide Neff Effective refractive index of the channel waveguide mode N~ Effective refractive index of the Z-polarized mode of the channel waveguide a~ Intermediate value of a length in x-direction a! Intermediate value of a length in y-direction a Width of the structure or the refractive index profile, respectively t Depth (height) of the structure or the refractive index profile, respectively w Starting width of the titanium strip for the indiffusion td Diffusion time x-y-z Coordinate system n~. Distribution of the refractive index in the waveguiding region n~,.,= f(x,y) n, Refractive index of the substrate n2 Refractive index of the waveguiding region at the surface n3 Refractive index of the superstrate ns Refractive index of the substrate if nl > n3 or refractive index of the supe~lrate if n3 > n, d(n2-ns)/ d~ Wavelength dependence (dispersion) of the increase of the refractive index necessary for optical waveguiding - 2187213 19~03 930.0-51 X 9597 Z Crystallographic Z-axis (or c-axis) ~o, .. , ~6 Wavelengths ;~a Shortest singlemode-guidable wavelength in the channel waveguide ~h oscillation build-up wavelength for the second mode in lateral direction in the widened coupling region ~min Minirnum wavelength of the optically transmitting range of a substrate material ~max Maximum wavelength of the optically transmitting range of a substrate material Discrete wavelengths ~, A~i Wavelength ranges ~, Bandwidth of channel waveguide . Wavelength range between the oscillation build-up of the fundamental mode Noo in the channel waveguide and the oscillation build-up of the second mode in lateral direction No2 in the widened coupling region of the junction splitter ~;~N Efficient usable wavelength region of the junction splitter ~E Bandwidth (spectrum) of light at the channel waveguide input ~;~A Bandwidth (spectrum) of light at the channel waveguide output Kii Element in the matri~ of intersection points

Claims (36)

Patent Claims

1. Junction splitter consisting of channel waveguides for the spatial combination or splitting or switching or deflection or modulation of light, in particular for applications within the wavelength range of visible light, comprising at least three channel waveguides, characterized by - at least one singlemode integrated-optical wideband channel waveguide(SOWCW) where in or on a surface-type substrate material (1), by means of a process for changing the refractive index, a channel-shaped structure can be fabricated or a channel-shaped structure made from a suitable material can be applied, with the geometric / substance parameters of the channel waveguide thus created being set in dependence of the wavelength ranges to be transmitted in the UV, visible, and/or IR regions, so that in relation to the wavelength (.lambda.) the minimum width of the wavelength range for singlemode light guidance is given by the equation .DELTA..lambda.w = 0.48 x .lambda. - 85 nm (with .lambda. and .DELTA..lambda.w being stated in nm), where the parameters substrate refractive index (n1), superstrate refractive index (n3), refractive index of the refractive index distribution (f(x,y)) on the surface (n2), refractive indexdistribution in the waveguiding region (nw = f(x,y)), cross-sectional shape (width a and depth t) of the channel waveguide and its location in and/or on the substrate are dimensioned such that singlemode operation of the channel waveguide in the wavelength range .DELTA..lambda.w > 0.48 x .lambda. - 85 nm (with .lambda. and .DELTA..lambda.w being stated in nm) is ensured, that is, to each given wavelength (.lambda.) in the range between .lambda.a and .lambda.a+.DELTA..lambda.w one and only one effective refractive index, i.e. the effective refractive index of the fundamental mode (N00), can be allocated, and the singlemode range will be determined by the efficient oscillation build-up, from a technical point of view, of fundamental mode N00 at wavelength .lambda.a+.DELTA..lambda.w on the one hand, and by the efficient oscillation build-up, from a technical point of view, of the first mode in lateral direction (N01) or of the first mode in depth direction (N10) at wavelength .lambda.a on the other hand, and with transmission at a technically sufficient degree of effectiveness signifying that the effective refractive index Neff of the mode guided in the channel waveguide must be at least 5x10-5 above the refractive index of the surrounding material ns, where ns designates the value of substrate index n1 or superstrate index n3, whichever is the greater, and with the minimum possible value of the usable wavelength (.lambda.min) and the maximum possible value of the usable wavelength (.lambda.max) being determined by the transmission range of the materials used, and thus the channel waveguide being defined as a singlemode integrated-optical wideband channel waveguide (SOWCW), and furthermore characterized by - the combination and connection of the minimum of three channel waveguides, in which the geometric / substance parameters of the channel waveguides themselves as well as the media surrounding the channel waveguides are set in dependence of the wavelength range to be transmitted in the UV, visible, and/or IR regions, so that in relation to the wavelength (.lambda.) the minimum width of the wavelength range for efficient junction splitter operation is given by the equation .DELTA..lambda.v = 0.27 x .lambda. - 34 nm (with .lambda. and .DELTA..lambda.v being stated in nm), where the parameters substrate refractive index (n1), superstrate refractive index (n3), refractive index of the refractive index distribution (f(x,y)) on the surface (n2), refractive indexdistribution in the waveguiding region (nw = f(x,y)), geometry of the junction splitter, and its location in and/or on the substrate are dimensioned such that efficient operation of the junction splitter is at least ensured in the wavelength range .DELTA..lambda.v > 0.27 x .lambda. - 34 nm (with .lambda. and .DELTA..lambda.v being stated in nm), with the usable wavelength range .DELTA..lambda.N
for the efficient operation of the junction splitter, technically seen, is determined by the lesser value of either - the difference between wavelength .lambda.a+.DELTA..lambda.w of the efficient oscillation build-up, from a technical point of view, of the fundamental mode (N00) in the channel waveguide and wavelength .lambda.a of the efficient oscillation build-up, from a technical point of view,of the first mode in lateral direction (N01) or of the first mode in depth direction (N10) in the channel waveguide, or - the difference between wavelength .lambda.a+.DELTA..lambda.w of the efficient oscillation build-up, from a technical point of view, of the fundamental mode (N00) in the channel waveguide and wavelength .lambda.b of the efficient oscillation build-up, from a technical point of view, of the second mode in lateral direction in the coupling area, widened in relation to the channel waveguide, of the junction splitter (N02), that is by .DELTA..lambda.N and thus the junction splitter consisting of at least three channel waveguides, comprising at least one SOWCW, is defined as an integrated-optical wideband junction splitter (Figure 6a, 6b).

2. Junction splitter according to Claim 1, in which - at least two channel waveguides (2,3) each have a respective input (E1,E2) into which light may be injected, and which are combined into a common channel waveguide at their outputs (A1,A2) in a coupling point (6), and where - the common channel waveguide is a singlemode integrated-optical wideband channel waveguide, that is, a SOWCW (5), which is provided with a common usable light output (AM) for spatially combined light.
(Figures 1a, 1b, 7, 8, 9, 10b, 10d).

3. Junction splitter according to Claim 1, in which - at least one channel waveguide (2) is intersected by at least one further channel waveguide (3), and where this minimum of one intersection point is a) fully passive, or b) a coupling point (6) for the spatial combination of light components, or c) a controllable coupling unit for the spatial combination of beams and/or deviation of beams (7), and furthermore - it is possible to inject light into each channel waveguide (2, 3), and - the common channel waveguide is a singlemode integrated-optical wideband channel waveguide, that is, a SOWCW (5), which is provided with a common usable light output (AM) for spatially combined light. (Figures 1c, 11, 12, 13)

4. Junction splitter according to Claim 1, in which - at least two channel waveguides (2, 3) each have a respective input (E1, E2) into which light may be injected, and in which - the minimum of two channel waveguides (2, 3) have an intersection point, and in which - at the intersection point of channel waveguide (2) and channel waveguide (3) an integrated-optical reflector (R2) is located, forming the coupling point (6), and in which - the common channel waveguide is a singlemode integrated-optical wideband channel waveguide, that is, a SOWCW (5), which is provided with a common usable light output (AM) for spatially combined light. (Figure 1d, 10f).

5. Junction splitter according to Claims 1 or 2 or 3 or 4, in which all channel waveguides are designed as singlemode integrated-optical wideband channel waveguides (SOWCW).

6. Junction splitter according to Claim 1, in which at least one channel waveguide consists of rubidium ? potassium ion exchanged potassium titanyl phosphate (KTiOPO4, KTP), where the geometric and substance parameters can be set such that a singlemode operation of the channel waveguide within the wavelength range .DELTA..lambda.w > 0.48 x .lambda. - 85 nm (with .lambda. and .DELTA..lambda.w being stated in nm) is ensured, this channel waveguide thus being a SOWCW, with the minimum possible value of the usable wavelength (.lambda.min approx.
350 nm) and the maximum possible value of the usable wavelength (.lambda.max approx. 4 µm) being determined by the optical transmission range of KTiOPO4, and with, in particular, the wavelength range (.DELTA..lambda.w) of theSOWCW to be transmitted in singlemode in the visible light wavelength spectrum comprising a wavelength range greater than 350 nm, and with the SOWCW being thus defined as a singlemode white light channel waveguide, and which in conjunction with two further channel waveguides forms a wideband integrated-optical junction splitter, and where in particular the usable wavelength range .DELTA..lambda.N for efficient operation of the junction splitter within the visible light wavelength range comprises a wavelength range greater than 300 nm, and with the junction splitter being thus defined as a white light junction splitter.

7. Junction splitter according to Claim 1, in which at least two channel waveguides (2, 3, ...) are connected at each input (E1, E2, ...) with one light source respectively (L1, L2, ...), and in which each light source emits light of a different wavelength (.lambda.1, .lambda.2, ...) or of different wavelength ranges .DELTA..lambda.1, .DELTA..lambda.2, ...).

8. Junction splitter according to Claim 1, in which at least one channel waveguide (2, 3, ...,5) is connected at its input (E1, E2, ....) or its output (AM) with at least one light source (L1, L2, ...), and in which each light source emits light of at least one wavelength (.lambda.1, .lambda.2, ...) or at least one wavelength range (.DELTA..lambda.1, .DELTA..lambda.2, ...) into at least one channel waveguide.

9. Junction splitter according to Claim 1, in which at least one channel waveguide (2, 3, 5) is provided with a modulation device (AM) which modulates, in dependence of the wavelength or wavelength-independently, phase, amplitude or intensity and/or polarization direction of light components.

10. Junction splitter according to Claim 1, in which - at least one of the light sources (L) themselves may be modulated in their performance, and/or - modulation can be effected by changing the coupling effectivity between light source and waveguide, or - modulation by means of light weakeners (e.g. wedge filter), or - phase shifters (e.g. Pockels cell), or - polarization converters in connection with a polarizing device or a polarizing channel waveguide.

11. Junction splitter according to Claim 1, in which the coupling point (6) created by combining the outputs (A1, A2) of the channel waveguides (2, 3) is a controllable unit for spatial beam combination and/or beam deviation (7), by means of which at least one of the light components (?, ?2) can be applied to the common SOWCW (5) and/or modulated. (Figures 1a, 1b, 1c, 1d).

12. Junction splitter according to Claim 1, in which the light components of at least two wavelengths (?, ?2, ...) may be injected as light pulses sequentially into one channel waveguide (2, 3, 4) each and can be spatially combined in the coupling point (6), and furthermore the spatially combined light components can be controlled in the common SOWCW (5) by a modulation device (amplitude modulator AM) in a pulsed cycle (time-multiplexed operation). (Figure 16)

13. Junction splitter according to Claim 11 and Claim 12, in which the minimum of one coupling point (6) is a controllable unit for spatial beam combination and/or beam deviation (7) by means of which the light pulses may be modulated synchronously and combined into the common SOWCW (5).

14. Junction splitter according to Claim 9 or Claim 11, in which the modulation device (AM) and/or the controllable unit for spatial beam combination and/or beam deviation (7) is based on one of the following principles:

modulation by electric fields, that is, electro-optical light modulation by means of an integrated-optical interferometer structure, modulation by pressure waves, that is, acousto-optical light modulation by means of an integrated-optical interferometer structure, modulation by heat, that is, thermo-optical light modulation by means of an integrated-optical interferometer structure, modulation by magnetic fields, that is, magneto-optical light modulation by means of an integrated-optical interferometer structure, modulation by light radiation, that is, opto-optical light modulation by means of an integrated-optical interferometer structure, modulation by heat radiation, that is, photo-thermal light modulation by means of an integrated-optical interferometer structure, modulation by electric charge carriers, that is, modification of the effective refractive index by injection or depletion of free charge carriers in semiconductor materials, in connection with an integrated-optical interferometer structure, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical, or photo-thermal modulation using the Fabry-Perot effect, modulation by changing the effective refractive index by means of injection or depletion of free charge carriers in semiconductor materials, using the Fabry-Perot effect, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical, or photo-thermal cut-off modulation, cut-off modulation on the basis of the change in the effective refractive index as a result of the injection or depletion of the free charge carriers in semiconductor materials, - controllable waveguide amplification, - controllable polarization conversion in conjunction with a polarizing device or polarizing channel waveguide, - waveguide mode conversion, - electro-absorption modulation, or - modulation with the assistance of an integrated-optical switching or distributor element, such as an X-coupler, three-guide coupler, directional coupler or BOA.

15. Junction splitter according to Claim 1, in which the combination and/or branching of the channel waveguides is effected according to at least one of the following principles:
- use of a Y-junction coupler, or - use of an integrated-optical switching and distributing element, such as an X-coupler or directional coupler or three-guide coupler, or - use of a device for two-mode interference in the channel waveguide (BOA), or - use of an integrated-optical and/or micro-optical reflector (mirror, grating, or prism).

16. Junction splitter according to Claim 1, in which on the surface-type substrate at least two channel waveguides run parallel in one direction and at least one further channel waveguide runs in another direction, and where the intersection points (6) of the channel waveguides form a matrix.

17. Junction splitter according to Claim 16, in which the matrix of the intersection points is set up according to the following principles:

- According to the number m of light components of wavelengths .lambda.i, where i = 2 to m, m channel waveguides (2, 3, 4) are run in parallel and intersect one SOWCW (8), and where - the intersection points are passive coupling points (6) for the spatial combination of beams and, if required, an amplitude modulator (AM) is arranged on each of the m channel waveguides (Figure 12), or - the intersection points are controllable units for the spatial combination of beams and/or deviation of beams (7). (Figure 11, Figure 13)

18. Junction splitter according to Claim 16, in which the matrix of intersection points K? is set up according to the following principles:
- According to the number m of light components of wavelengths .lambda.i, where i = 1 to m, and m 2, m channel waveguides (2, 3, 4, ...) are run in parallel, and n-1 further channel waveguides (8', 8", 8"' ...) and an SOWCW (5) intersect the m channel waveguides, and are also run in parallel, with their number n = m+1, and where - the intersection points Kij for i = j are controllable units for the spatial combination of beams and/or deviation of beams (7), - the intersection points Kij for i = 1 to m and j = n = m+1 are passive coupling points (6), and - the other intersection points are fully passive, and furthermore - the j = 1 to n-1 channel waveguides (8', 8'', 8''',....) are blind outputs, and - the j = m channel waveguide is the common SOWCW (5) for the spatially combined light. (Figure 13)

19. Junction splitter according to Claim 8, which provides for operation in splitting direction by means of coupling the common SOWCW
(5') to a light source emitting light of wavelength ?0 or light of a wavelength spectrum (.DELTA.?), and with the common SOWCW (5') ending in a coupling point (6'), from which coupling point (6') at least two channel waveguides (2, 3) start, in which channel waveguides the coherent light of wavelength ?0 or the wavelength spectrum (.DELTA.?) can be guided. (Figure 10a, 10c, 10e, 17c).

20. Junction splitter according to Claim 1, where, in at least one channel waveguide (2, 3, 4), a frequency converter (FU) based on non-linear optical effects is located ahead of the coupling point (6) for spatial light combination. (Figures 21, 22)

21. Use of a wideband junction splitter as a device for spatially combining the light of at least two differing wavelengths (?i) or wavelength ranges (.DELTA.?j) for generating fast-changing spectral compositions of light, in particular for colour mixing, in a usable spectrum range greater than 75 nm, in which the minimum of two light components are injected, respectively, into one channel waveguide each, and decoupled from a common SOWCW (5) as spatially combined light. (Figures 1 and 7 to 22)

22. Use of a wideband junction splitter as a device for the splitting of light (?i, .DELTA.?i) into at least two light components in a usable spectrum range greaterthan 75 nm, in which the minimum of one light component is injected into an SOWCW (5'), and in which light components from at least two channel waveguides, which have the same spectral composition and phasing as the injected light, are decoupled. (Figures 8, 17c, 18, 19b, 20, 22)

23. Application of the wideband junction splitter as a wavelength-selective or wavelength-independent wideband switch or wideband modulator for the amplitude or intensity of light of at least one wavelength or one wavelength range for generating fast changing light intensities and/or spectral light compositions in a usable spectrum range greater than 75 nm, in which light is injected into at least one channel waveguide and decoupled at a common SOWCW (5) as spatially combined modulated light. (Figures 7, 8, 9, 11, 12, 13, 19)

24. Application of the wideband junction splitter according to Claim 23 as a wavelength-selective wideband switch or wideband modulator, in particular as a controllable colour filter, implemented on the basis of one of the following principles:
- electro-optical modulation - acousto-optical modulation - thermo-optical modulation - magneto-optical modulation - opto-optical modulation - photothermal modulation change of the effective refractive index by injection or depletion of free charge carriers in semiconductor materials, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical, or photothermal modulation utilizing the Fabry-Perot effect, modulation by changing the effective refractive index by injection or depletion of free charge carriers in semiconductor materials, utilizing the Fabry-Perot effect, electro-optical, acousto-optical, thermo-optical, magneto-optical, opto-optical, or photothermal cut-off modulation, cut-off modulation due to the change in the effective refractive index by injection or depletion of free charge carriers in semiconductor materials, controllable waveguide amplification, controllable polarization conversion, waveguide mode conversion, or furthermore a phase shifter (e.g. Pockels cell), or polarization converter in connection with a polarizing device or polalizing waveguide as external device.

25. Use of the wideband junction splitter according to Claim 23 in a device as a wavelength-independent wideband switch or wideband modulator, in which modulation is implemented on the basis of one of the following principles:

electro-absorption modulation - changing the coupling effectivity between light source and waveguide, - modulation of the light source itself, or furthermore - light weakeners (e.g. wedge filter), as an external device.

26. Use of a wideband junction splitter according to Claim 23 in an arrangement as wideband interferometer device, in particular as a wideband Mach-Zehnder interferometer device, in which light of one wavelength or one wavelength range is injected into a common SOWCW
(5'), and in which the light in the SOWCW (5') is split at a coupling point (6') and passed on in separate SOWCW (2 and 3), and in which furthermore the light in the SOWCW (2 and 3) is spatially combined at a coupling point (6) and decoupled at output (AM) of the common SOWCW
(5), and where in the area of the separately guided SOWCW (2, 3) an electric field is generated by electrodes (10), in which the light in at least one SOWCW (2, 3) is influenced as regards its phasing, and/or amplitude, and/or polarization direction.
(Figures 8, 17, 18, 19, 20)

27. Use of a wideband junction splitter in an arrangement as a measurement device for physical, chemical, and biological parameters, in which - a light component in a channel waveguide or SOWCW (2, 3), or - the spatially combined light (M) in a common SOWCW (5), or - the spatially combined light provided at output (AM) of the SOWCW
(5), or - the waveguiding in one of the charmel waveguides or SOWCW (2, 3) or SOWCW (5) are influenced by a parameter, and in which the spatially combined light components (M) are measured photometrically at a point after output (AM) of the common SOWCW (5).

28. Use of the wideband junction splitter according to Claim 27 in an arrangement as distance difference measurement device, in which, by means of an interferometrical procedure, shifts in an object to be tested are measured.
(Figure 23)

29. Use of the wideband junction splitter according to Claim 27 in a photometrical arrangement, in which the spatially combined light components of at least two wavelengths correspond to a medium to be measured, either simultaneously or consecutively, and the changes in light intensity due to changes in, e.g., reflection, transmission, or scattering are measured for each used wavelength of the light components. (Fig. 14, 15, 20)

30. Use of the wideband junction splitter according to Claim 27 in an arrangement as wavelength sensor, in which light of an unknown wavelength is injected into the common SOWCW
(5'), the common SOWCW (5') is split into two SOWCW (2 and 3), and these SOWCW (2, 3) are spatially combined in a comrnon SOWCW (5), and which thus constitutes an integrated-optical interferometer structure, with the light intensity being measured at output (AM) of the common SOWCW
(5), and electrodes being fitted in some suitable fashion on the SOWCW (2, 3), and with the height of the voltage applied to the electrodes - which voltage causes a change in the light transmission performance at output (AM) from maximum to an adjacent minimum, or vice versa - being a measure for the wavelength of the light. (Figure 18)

31. Use of the wideband junction splitter according to Claim 27 in an arrangement as a sensor, in which the substrate surface carrying the channel waveguides or SOWCW, is covered, leaving only an interaction window (15), which interaction window (15) covers the SOWCW (5), and where - the medium to be measured (16) is brought into direct contact with the SOWCW (5), via the interaction window (15), or - the surface of the interaction window (15) is coated with a specific sensitive material, which is in contact with the medium to be measured (16), and where light parameters are measured at the output of the common SOWCW (5), which characterize the specific properties of the test medium (16).
(Figure 15).

32. Use of a wideband junction splitter according to Claim 31, in which light of at least two wavelengths (.lambda.i) is spatially combined in the wideband junction splitter, and the common SOWCW (5) is not covered at an interaction window (15) only. (Figure 15)

33. Use of the wideband junction splitter according to Claim 31 in an arrangement for determining the refractive index, in which light of at least two wavelengths (.lambda.i) is spatially combined in the wideband junction splitter, and then the spatially combined light (M) is passed into a Mach-Zehnder interferometer structure (MZI), in the one waveguide branch of which interferometer structure the electrodes (10) are located for phase modulation, and in the other waveguide branch of which interferometer structure an interaction window (15) is located. (Figure 20)

34. Use of the wideband junction splitter as wavelength-selective or wavelength-independent wideband switch or wideband modulator of phasing and/or the polarization direction of light of at least one wavelength (.lambda.i) or a wavelength range (.DELTA..lambda.i) for generating fast changing phasing and/or polarization directions, in a usable spectrum range greater than 75 nm, in which light is injected into at least one SOWCW (2, 3) and decoupled at an output (AM) of the common SOWCW (5) as spatially combined modulated light (M).

35. Use of the wideband junction splitter in an arrangement as frequency converter, in which at least one frequency conversion device (FU) is located in at least one channel waveguide, and in which frequency conversion device the wavelength of the light component injected into the channel waveguides (2, 3) is changed, and where combined light components with at least one altered wavelength are applied to the output of the common SOWCW (5). (Figure 21, 22)

36. Use of the wideband junction splitter according to Claim 35 in which the light of one wavelength is injected into a common SOWCW (5'), the common SOWCW (5') is split into at least two channel waveguides or SOWCW (2, 3), in each waveguide branch a frequency conversion device (FU) is located, and the converted light components are spatially combined and applied at output (AM) of the common SOWCW (5).