DE102005008077B4 - Radiator, and device and method for analyzing the qualitative and / or quantitative composition of fluids with such a radiator - Google Patents

Abstract

spotlight, in particular thermal radiator in the infrared spectral range, with a photonic crystal (10, 20, 30), wherein the radiation by local temperature change exclusively in a partial region (13, 23, 73) of the photonic crystal (10, 20, 30) can be generated.

Description

The The present invention relates to a radiator, in particular a thermal radiator in the infrared spectral range and a device and a method of analyzing the qualitative and / or quantitative Composition of fluids with such a radiator.

For the qualitative and / or quantitative analysis of the composition of fluids (ie gases or liquids) optical measuring methods are often used. A common measuring method is absorption spectroscopy, which is based on a specific absorption of electromagnetic radiation of defined wavelength ranges by the various components of the fluid. Thus, many gases, such as CO, CO ₂ or CH ₄ , absorption lines, especially in the infrared range. A special form of absorption spectroscopy is photoacoustics (PAS), in which the absorption is acoustically detected by a pressure change.

by virtue of the strong and molecule-specific spectral absorption structures in the mid-infrared range (with a wavelength from 3 to 20 μm) This spectral range is particularly suitable for sensitive detection or an analysis method.

In The rule will be for this for cost reasons used thermal infrared radiator. However, a spectral Power density of thermal infrared radiators through the Planck curve physically limited. Because of this low efficiency the available standing light sources is a detection strength of such analysis methods and analyzers determined and limited.

Laser light sources or other coherent radiation sources are for most applications too expensive or too expensive. This is especially true for the long-wave part of the middle infrared, e.g. in the range around 10 μm wavelength. This Spectral range is also called "fingerprint range" because there characteristic absorption bands of many compounds.

Especially In this spectral range, an efficient light source is desirable.

It is therefore an object of the present invention, an efficient Light source, in particular an efficient thermal radiator, available too put.

These The object is achieved by a radiator with the features of claim 1.

By The present invention is based on a novel radiator photonic crystals available posed.

The local temperature change can by an inductive and / or resistive heating of the sub-area of the photonic crystal be generated.

According to one preferred embodiment has the present radiator in the pores of the subregion of a photonic crystal introduced magnetic material which is inductive, in particular via at least one on a surface of the photonic crystal arranged induction coil is heated.

According to one another preferred embodiment has the present radiator in the pores of the subregion of the photonic crystal introduced, electrically conductive, in particular semiconducting or metallic material, which by direct current flow through contacts on the surface of the photonic crystal and / or inductively via a magnetic alternating field is heatable.

Of the Photonic crystal can be one-dimensional, two-dimensional or three-dimensional or be formed as a photonic hollow fiber.

Of the photonic crystal can also be formed from a material, which has a good transmission property in the mid-infrared range having.

moreover It is advantageous if the photonic crystal of a material be formed, which has a temperature resistance at least up to 1000 K has.

Furthermore, the photonic crystal may be formed of macroporous silicon, SiO ₂ , or AL ₂ O ₃ , or Ge, chalcogenide glass, BaF ₂ , CaF _2, or carbon.

According to a further preferred embodiment of the radiator is the magnetic and / or electrically conductive material to be introduced into the pores of the photonic crystal, for example Fe, Ni, Pt, Ta or W by infiltration of a liquid solution or melt or by layered deposition such as PVD or CVD Method can be introduced into the predefined photonic structure. The magnetic and / or electrically conductive to be introduced into the pores of the photonic crystal However, material can also be introduced by admixtures during crystal growth during the production of the photonic crystal.

optical Measuring instruments for determination The composition of fluids are often discrete components composed, i. they consist of a spotlight, an imaging optics, a measuring cell, a detection optics and a detector element and the associated drive and evaluation electronics. For However, a compact sensor should integrate these individual components as much as possible, i.e. ideally on a common substrate (e.g., a semiconductor chip) available.

Especially disadvantageous in the known optical measuring devices with discrete components is that the Infrared light emanates from the radiator before an interaction with the gas in a gas filled cavity takes place. In addition, most of the space is the interaction between gas and radiation is not designed as a special waveguide.

From the publication DE 100 63 151 A1 For example, a compact measuring arrangement is known in which an interaction section for the interaction of electromagnetic radiation and fluid is designed as a reduced group velocity photonic crystal for certain light propagation directions and wavelengths of light. This interaction section may be part of a waveguide.

For example, it may be advantageous to insert the photonic interaction section into matched ("tapered") waveguide structures to achieve good light coupling into the interaction section DE 100 63 151 A1 a separate light source is provided which does not form an integral part of the photonic crystal. Accordingly, the infrared radiation from the light source is emitted and must be coupled into the waveguide (as part of the photonic crystal).

In Photonic structures are added in defined spectral regions increased radiation intensities the emission of heated structures versus unstructured emitters have been watching. At the exit of the radiation from the photonic Crystal will be lifted but these benefits again. Therefore - while for certain wavelength and propagation directions in a photonic crystal due the special photonic wall structure an increased photonic Density of states as in a classic black body radiator is present - in the Decoupling the radiation, this density of states back to the one Black body radiator reduced. Consequently, it is not possible in principle a suitable structuring of the thermal emitter material a light bulb with higher total and spectral radiance as a classic black body radiator to realize at the same temperature.

It Therefore, another object of the present invention is a method and a device for analyzing the qualitative or quantitative composition of fluids to be used for the detection of the composition the fluids necessary radiation generated in an effective manner is.

The The above object is in device-technical terms a device with the features of claim 10 solved. In process engineering The above object is achieved by a method with the Characteristics of claim 23 solved.

The inventive method and the device according to the invention characterized in particular by the fact that the light production of broadband IR light is already made in the waveguide structure. In order to Also, the generated radiation is in a photonic waveguide structure leave and there for used the detection of the composition of fluids. Accordingly becomes the aforementioned radiator in the device according to the invention and the method of the invention so used that Infrared light from generation to detection in a suitable (preferably photonically structured) waveguide structure is guided. Accordingly, with the present invention, a selective incoherent Light source for created the analysis of the composition of fluids. hereby become highly sensitive, compact and specific gas and liquid sensors allows those in production and process measuring technology, in the automotive sector, can be used in safety technology and in climate and environmental sensors are.

preferred embodiments the device according to the invention are in the dependent claims 11th to 22 listed. Preferred embodiments of the method according to the invention in the dependent claims 24 and 25 listed.

The The present invention will be described below with reference to preferred embodiments in conjunction with the associated Drawings closer explained. In these show:

1 a schematic representation of an embodiment of the present radiator with a two-dimensional, inductively (locally) up heated photonic crystal,

2 a schematic representation of another embodiment of the present radiator with an electrical (local) heating of the photonic crystal,

3 a schematic representation of a measuring arrangement with parallel measuring and reference channels, and

4 a schematic representation of another embodiment of a measuring arrangement with a measuring channel and an electric heating control (at constant temperature) in conjunction with a measurement of the electrical power consumption at this constant temperature.

1 schematically shows a section of a two-dimensional photonic crystal 10 for forming the selective incoherent light source via a thermal radiator in the infrared spectral range.

In the present case, in the base material of the photonic crystal (for example, a Si wafer), columnar regions are used 11 is formed, whereby a periodic dielectric structure is formed, whose period length is set so that they influence the propagation of electromagnetic waves in a similar manner as the periodic potential in semiconductor crystals, the propagation of electrons. This creates - analogous to the formation of the electronic band structure - a photonic band structure, which has areas of forbidden energy, in which electromagnetic waves can not propagate within the crystal (photonic band gaps).

In the two-dimensional structure of the photonic crystal shown here 10 are the regions of increased or decreased refractive index in the form of columns 11 represented, which are also referred to as pores. Particularly suitable for this purpose is macroporous material which can form both two-dimensional and three-dimensional photonic crystals. A wall of pores is in 1 with the reference number 12 exemplary picked out.

Instead of the illustrated two-dimensional photonic structure (e.g. a wafer made of macroporous Silicon) may also have a one-dimensional photonic structure (e.g. an interference filter structure) or a three-dimensional photonic Structure (e.g., an infiltrated opaline structure). As well Is it possible, to form the photonic crystal as a photonic hollow fiber.

As materials for the photonic crystal, it is preferable to use macroporous silicon, SiO ₂ , or AL ₂ O ₃ . Likewise, materials such as Ge, chalcogenide glasses, BaF ₂ and CaF ₂ or carbon (eg diamond-like layers) can be used.

In the 1 shown photonic structure is shown as open-pore structure. In addition to the training as an open-pored structure, however, the training as completely or partially coated and thus closed to the environment structure is possible.

at In a mid-infrared application, the materials must have a good Have infrared transmission.

Good transmission properties are present at a transmission through the entire material of greater than 10%, ie at an absorption constant of the material of α less than 0.1 cm ^-1 in the spectral range of the mid-infrared, for example 3-12 microns wavelength or in by the respective application specified partial spectral ranges, such as 4.2 to 4.3 microns for CO ₂ detection. A comparatively poor IR transmission is present at an absorption constant of α less than 10 cm ^-1 .

In addition, the Materials at least in the heated area a sufficient temperature resistance, preferably to at least about 1000 K, have.

In the hatched areas 13 the pores 11 according to the embodiment in 1 a magnetic material is arranged, ie the pores 11 are partly with the magnetic material 13 met or coated with this. Adjacent to the photonic crystal 10 and in particular adjacent to the (partially) filled with magnetic material or coated pores 11 is at least one induction coil 14 arranged.

By means of the induction coil 14 an alternating magnetic field is applied to the photonic crystal at least locally, wherein the alternating magnetic field interacts with the magnetic material in the pores and energy of the alternating magnetic field is coupled into the magnetic material.

The magnetic material is via the inductive heating by means of the induction coil 14 locally heated to high temperatures (about 1000 K). The heated volume of material is preferably <10 ^-3 mm ³ . The photonic crystal 10 is therefore designed such that the heating due to the (low) thermal conductivity of the crystal remains locally limited.

A low thermal conductivity indicates For example, Al ₂ O ₃ ceramic with a Wärmeleitkoeffizienten λ less than 10 W / (m · K) on. For porous silicon, λ values of less than 0.5 W / (m · K) are called. In the present case, "low" means that the heat conduction coefficient λ is less than 10 W / (m · K). In contrast, with a heat conduction coefficient with λ greater than 100 W / (m · K), it can be said that the thermal conductivity is "good". For example, silicon has a λ value of 148 W / (m · K) and copper has a λ value of 393 W / (m · K).

According to a further preferred embodiment (which in 2 is shown) become pores of a portion of the photonic crystal 20 with a metallic material 23 (partially) filled or coated. At the top and / or bottom of the photonic crystal 20 are opposite to the metallic material filled or coated pores electrical contacts 24 arranged. By means of direct current flow via the electrical contacts 24 The electrically conductive material is heated resistively in the pores.

at Materials that are electrically conductive and magnetic at the same time Properties may have electric and magnetic heating can be used cumulatively. Likewise, the Pores partially with an electrically conductive material and partially be filled / coated with a material having magnetic properties.

In the present case, only a part of the photonic crystal is used 20 with the electrically conductive material 23 or with the magnetic properties having material 13 provided and generates a local warming.

At the in 2 shown embodiment of the radiator are at least the filled with the electrically conductive material pores 23 by means of an electrically conductive layer containing the contacts 24 forms, coated.

According to the embodiment according to 2 In addition, the openings of the (not filled with the electrically conductive material) pores are beyond 21 coated, reducing the pores 21 Completed towards the environment.

Of the photonic crystal can according to a special embodiment also be designed as photonic hollow fiber ("photonic crystal crystal", "PCF"). The heatable portion of the photonic structure is according to this particular embodiment a correspondingly modified, i. with a magnetic or electrically conductive material filled Section in the hollow fiber. The electromagnetic heating will thereby made by the fact that the corresponding fiber section is introduced into a coil.

With the formation as a photonic hollow fiber, a waveguide is provided, whereby the light source and the interaction section executed in detail below 50 can be arranged with a greater distance from each other. For example, the radiation generated over several meters without coupling or decoupling operations are forwarded before it comes to the interaction of the radiation with the fluid to be detected.

The magnetic and / or electrically highly conductive, preferably metallic, to be heated materials (such as Fe, Ni, Pt, Ta, W), for example by infiltrating a suitable liquid solution or melt or by layered Deposition such as PVD, or CVD method in the previously defined photonic Structure introduced. It is also possible, the material to be heated already in the production of the photonic crystal by appropriate Add admixtures in the crystal growing.

The Abbreviation "PVD" stands for "physical vapor deposition ", i.e. So for Coating methods such as vapor deposition or sputtering. The abbreviation for "CVD" stands for "chemical vapor deposition ". Important CVD methods of microtechnology are in particular APCVD (Normal Pressure Method / Atmospheric Pressure CVD at atmospheric pressure and T ≈ 1000-1300 ° C), LPCVD (Low pressure method / low pressure CVD at p = 0.01-10 mbar and T = 500-1000 ° C), and PECVD (Plasma CVD / Plasma Enhanced CVD at p ≈ 1 mbar and T = 200-500 ° C). At APCVD and LPCVD, activation of the reaction occurs thermally by heat PECVD by heat and electron impact in the Plasma of low pressure discharge.

In 3 an embodiment of the apparatus for analyzing the qualitative and / or quantitative composition of fluids is set out schematically in its basic features.

The photonic crystal 30 is present from a macroporous material, eg. As a Si wafer formed. At the top and bottom of the Si wafer 30 each is a substrate layer 35 of SiO ₂ , for example, arranged around a wide area of the top and bottom of the photonic crystal 30 Cover, ie to close the end faces of the pores of the Si wafer. These areas, which with the SiO ₂ layer 35 are a passive part, ie, a pure waveguide region, of the photonic crystal.

The at least partially filled / coated pores with the heatable material 33 make that Spotlight, as an integral part of the photonic crystal 30 , In the area of the front sides of the filled with heatable material pores 33 can electrical contacts 24 (as in 3 shown). Alternatively, the pores 33 also be finished with a substrate, such as SiO ₂ frontally, if a heating of the in the pores 33 arranged heatable material is inductively. For the mode of action of the radiator, the ability to locally heat the photonic crystal is crucial.

The emitted by the radiator radiation is in the passive part of the photonic Crystal forwarded. The passive part of the photonic crystal accordingly forms a photonic waveguide structure.

In 3 is on the left side a first detector element 40 arranged with which emitted by the radiator and in the waveguide structure forwarded radiation is detectable. The radiation emitted by the radiator is transmitted in the waveguide structure and impinges on the first detector element without interaction with the fluid to be detected 40 , Accordingly, the first detector element forms 40 a reference channel to the below explained in detail measuring channel.

The measuring channel has an interaction section 50 in which the fluid interacts with the radiation emitted by the radiator. In 3 is the interaction section 50 formed as part of the photonic structure, wherein the photonic crystal is open-pored in the region of the interaction section. In other words, in the area of the interaction section, the surface of the Si wafer is "open", ie there is no substrate layer, such as the above-described SiO ₂ layer, provided on the top or bottom, respectively the fluid, as indicated by the arrows A, enforce the photonic structure.

The measuring channel comprises the interaction section 50 which is penetrated by the fluid and a (further) detector element 60 , The fluid is a compressible medium, ie a gas. Accordingly, the interaction section 50 The gas-permeable waveguide part. After the radiation, the interaction section 50 has passed through the radiation via another passive waveguide to the (further) detector element 60 fed. About the second detector element 60 a modified spectrum is measured in which the absorption bands of the components of the gas are mapped.

at gaseous Fluids, the open-pore structure described above is advantageous. For one Liquid proof in which the media exchange due to the lower viscosity of the fluid to gases is reduced, the photonic waveguide can also be formed be that interaction with the fluid over the evanescent field on the surface of the waveguide happens.

The radiation detectors 50 . 60 can be formed integrated into the photonic crystal.

Of the Photonic crystal is designed such that the broadband emission spectrum the spotlight only for a defined narrow wavelength range is forwarded and after irradiation of the interaction section in the photonic crystal, hits the detector. Become light of other emission wavelengths not passed on by the photonic crystal or only with very high attenuation.

According to the in 3 shown embodiment, the measuring channel is supplemented by a reference channel, which is not flowed through with fluid. The reference channel has a detector element, by means of which the radiation power of the radiator is measured. For a detection of the fluid, or the components in the fluid, the ratio between the two detector signals, ie the signal of the measuring channel and the signal of the reference channel, evaluated.

A particular embodiment of the present device is a measuring arrangement in which the heating power of an integrated radiator is determined in a photonic crystal. Such a measuring arrangement is in 4 shown.

at Detection of a gas is in the waveguide the radiation through the Gas absorbed. This results in a higher heating capacity for compliance a fixed jet temperature necessary. For gas detection is either the radiator temperature measured at a fixed heat output or it is controlled to constant radiant temperature and the necessary heating power certainly.

at this method occurring disturbing influences, such as the ambient temperature or fluctuations in the gas flow, through the use of a reference measurement, for example via a other spectral channel (described in more detail below) excluded become.

According to the in 4 shown embodiment of the photonic crystal 70 with the pores 71 is a part of the pores 73 met with an electrically conductive material. About the contact surfaces 74 which are made of the same material, which the pores 73 is satisfied, this portion of the photonic crystal is part of an electrical circuit. In this electrical circuit is a device for electrical heating control for constant temperature 80 arranged, with a performance of the device 80 over the power meter 81 is measurable. The interaction region is again indicated by the arrows A.

The passive waveguide regions of the photonic crystal are formed by the substrate layers formed in particular from SiO ₂ 75 completed against the environment.

At the end faces of the photonic crystal 70 are reflective coatings 80 arranged over which the radiation is reflected or dissipated.

A another particular embodiment of the present measuring arrangement is the use of two different waveguide structures and radiators, but if sufficiently thermally and optically decoupled, can be realized on a wafer. By different Grating periodicities of Both waveguides reach different spectral channels, the be absorbed differently from the target fluid. In a (reference) branch the radiation is not absorbed by the gas. In the other branch, the actual measuring channel, the radiation is absorbed by the gas. It will be the ratio of evaluated in both branches detected lines.

According to one another particular embodiment a pulsed radiator is used. The radiator cools after a pulsed warming the same by heat conduction in photonic crystal. Part of this heat dissipation also comes through the measuring gas which flows through the open part of the crystal. absorbs the gas efficient the radiation, this cooling effect is greater. This is the cooling curve the radiator (i.e., the heater) and the timing of the Power to a radiation detector is a measure of the presence of the measurement gas.

at In this method, the reference branch becomes possible for compensation Disturbances like the Ambient temperature used.

According to one Another embodiment is the radiation detector is designed as a photoacoustic cell. This is due to the heated gas in the measuring cell a pressure change causes the pressure change over a Microphone is detected. The gas-flow part of the photonic waveguide is at the same time part of an acoustic resonator, the (Periodic due to a modulated radiator temperature) Gas pressure fluctuations resonantly amplified. The microphone is located in doing so in / on the sound box.

As explained above, can use as a photonic crystal also a photonic hollow fiber Find. In such a photonic hollow fiber, it is advantageous if several interaction sections along the hollow fiber in a row are arranged. The radiation of the integral radiator passes along the hollow fiber of several measuring sections, before the power is detected at the detector element.

The Embodiments described above is the use of an integral selective incoherent emitter with photonic structuring in common, resulting in an improved Determination of the composition of fluids is achievable. there As a significant physical effect is the increased light intensity for certain propagation directions and wavelengths heated photonic crystals used. Unlike lasers, which have a monochromatic emission (defect laser) is Here, however, a comparatively broadband emission, as in realized spectrally filtered thermal radiation.

With The embodiments described above can be compact, efficient and cost effective liquid and gas sensors are realized. The electrical power consumption is less than conventional Sensors. This is especially for a distributed sensor or for self-sufficient (For example, solar-powered) sensor systems of crucial Advantage. Compact IR sensors can even be used in modern ones Include logistics and security concepts, such as The supervision of food transports, fire protection, etc.

Especially consists of using an integrally formed in the waveguide Light source of the advantage that the Temperature on the outside of the sensor is lower than previous solutions. Accordingly, such active IR sensors even in the ex-protected Be used area.

In the present case, therefore, an IR radiator is provided, which is integrally formed in a one- to three-dimensional photonic crystal. This is characterized by the fact that the emission is incoherent and broadband. However, the emission can also be spectrally selective, ie not as wide as a Planck curve. The radiation is generated by inductive or resistive heating of a region in the photonic crystal. In addition, the radiator can be integrated in a waveguide. In this case, the detection section for the fluid can be integrated in the waveguide. The present novel radiator on Ba This photonic crystals is used in the measuring arrangement so that the infrared light is guided from the generation to the detection in a suitable, preferably photonically structured waveguide structure. In particular, the light generation of broadband IR light is already made in the waveguide structure, whereby the radiation can be used effectively (since left in the photonic crystal) and for the detection of the merging of fluids.

Claims (25)

Radiator, in particular thermal radiator in the infrared spectral range, with a photonic crystal ( 10 . 20 . 30 ), whereby the radiation by local temperature change exclusively in a partial area ( 13 . 23 . 73 ) of the photonic crystal ( 10 . 20 . 30 ) is producible. Radiator according to claim 1, characterized in that the local temperature change by an inductive and / or resistive heating of the sub-area ( 13 . 23 . 73 ) of the photonic crystal ( 10 . 20 . 30 ) is producible. Radiator according to claim 2, characterized by a in the pores of the subregion ( 13 ) of the photonic crystal ( 10 ), magnetic material, which is inductive, in particular via at least one on a surface of the photonic crystal ( 10 ) arranged induction coil ( 14 ), is heatable. Radiator according to claim 2 or 3, characterized by a in the pores of the subregion ( 23 ) of the photonic crystal ( 20 ) introduced, electrically conductive, in particular semiconducting or metallic material which by direct current flow via contacts ( 24 ) on the surface of the photonic crystal ( 20 ) and / or inductively heatable via a magnetic alternating field. Radiator according to at least one of Claims 1 to 4, characterized in that the photonic crystal ( 10 . 20 . 30 ) is one-dimensional, two-dimensional or three-dimensional or formed as a photonic hollow fiber. Radiator according to at least one of claims 1 to 5, characterized in that the photonic crystal ( 10 . 20 . 30 ) is formed of a material having a good transmission property in the mid-infrared region. Radiator according to at least one of Claims 1 to 6, characterized in that the photonic crystal ( 10 . 20 . 30 ) is formed of a material which has a temperature resistance at least up to 1000 K. Radiator according to at least one of claims 1 to 7, characterized in that the photonic crystal ( 10 . 20 . 30 ) is formed from macroporous silicon, SiO ₂ , or Al ₂ O ₃ , Ge, chalcogenide glass, BaF ₂ , CaF ₂ , TiO ₂ , ZnO ₂ , SiC or carbon. Radiator according to at least one of claims 1 to 8, characterized in that in the pores ( 13 . 23 . 73 ) of the photonic crystal ( 10 . 20 . 30 ) to be introduced magnetic and / or electrically conductive material, for example Fe, Ni, Pt, Ta, SiC, Fe ₂ O ₃ , Fe ₃ O ₄ or W, by infiltration of a liquid solution or melt or by layered deposition such as PVD or CVD method can be introduced into the previously defined photonic structure, or that they can be introduced by admixtures in the crystal growth in the production of the photonic crystals. Device for analyzing the qualitative and / or quantitative composition of fluids with a radiator according to at least one of the claims 1 to 9, an interaction section ( 50 ) between fluids and radiation generated by the radiator and at least one radiation detector ( 40 . 60 ) for detecting an interaction between fluid and radiation, wherein the photonic crystal ( 30 ) of the radiator is formed as part of a waveguide section. Device according to Claim 10, characterized in that the interaction section ( 50 ) in the photonic crystal ( 30 ) of the radiator waveguide portion is formed, wherein the radiation in the photonic crystal ( 30 ) and in this to the interaction section ( 50 ), and wherein the radiation is the interaction section ( 50 ) penetrates. Apparatus according to claim 10 or 11, characterized in that the waveguide section at least in the region of the interaction section ( 50 ) has an open-pore structure, wherein the fluid to be examined the interaction section ( 50 ) flows through. Apparatus according to claim 10 or 11, characterized in that the waveguide section at least in the region of the interaction section ( 50 ) is designed such that an interaction of radiation with fluid takes place via an evanescent field. Device according to at least one of the claims 10 to 13, characterized in that the at least one radiation detector ( 40 . 60 ) in the photonic crystal ( 30 ) Waveguide section is integrated. Device according to at least one of the Pa tentansprüche 10 to 14, characterized in that the photonic crystal ( 30 ) is designed such that forward the radiation emitted by the radiator only for a defined narrow wavelength range. Device according to at least one of the claims 10 to 15, characterized by a reference channel, not flowed through by fluid, to which by means of the interaction section ( 50 ), wherein a radiation power of the reference channel with a second radiation detector ( 60 ) and a ratio between the detector signals of the measuring channel and the reference channel can be evaluated. Device according to at least one of the claims 10 to 16, characterized by a device ( 80 . 81 ) for controlling and / or measuring a heat output of the radiator, wherein a radiator temperature at fixed heating power is measurable, or wherein the radiator is regulated to a constant radiator temperature and the heating power necessary for this purpose can be determined. Device according to at least one of the claims 10 to 18, characterized by two spectral channels, which different, thermally and optically decoupled waveguide structures with integrated Emitters and have different grating periodicity. Device according to claim 18, characterized that the two spectral channels are arranged on a wafer. Device according to at least one of the claims 10 to 19, characterized by a pulsed heating of the radiator in conjunction with a subsequent cooling down of the photonic crystal. Device according to at least one of the claims 10 to 21, characterized in that the Interaction section for forming a photoacoustic measuring cell component an acoustic sound box is, wherein a radiator temperature can be modulated and thereby occurring gas pressure fluctuation is resonantly amplified. Device according to at least one of the claims 10 to 22, characterized in that along the waveguide multiple interaction sections are arranged. Method for analyzing the qualitative and / or quantitative composition of fluids, with one as photonic Crystal trained waveguide heated locally, from the heated Radiated radiation emitted in the waveguide, the Radiation in a section of the waveguide with at least one Fluid interacts and the radiation is subsequently detected. Method according to claim 23, characterized that this detected signal, the radiation interacting with the fluid compared with a reference signal of a second waveguide becomes. Method according to claim 23 or 24, characterized characterized in that a Radiator temperature is measured at a fixed heat output or that the radiator regulated to constant radiator temperature and the required heating power is determined.