Radiation source and gas sensor using the same

Abstract

A radiation source (10) for obliquely emitting narrowband electromagnetic radiation (11) into a cavity (12), comprising: an emitter structure (14), the emitter structure (14) having a main radiation emission area (14-1) for emitting the narrowband electromagnetic radiation (11), wherein the emitter structure (14) is optically coupled to the cavity (12); and a layer element (18), the layer element (18) being coupled to the main radiation emission area (14-1) of the emitter structure (14), wherein the layer element (18) comprises a radiation deflection (distortion) structure (20) configured for deflecting a radiation emission characteristic of the emitter structure (14) relative to a surface normal of the main radiation emission area (14-1) of the emitter structure (14).

Description

Technical Field

[0001] Various embodiments of the present disclosure relate to the field of radiation sources, for example, for gas detection. More specifically, various embodiments relate to the field of radiation sources for obliquely emitting narrowband electromagnetic radiation, for example, into a cavity. Alternative embodiments also relate to the field of gas sensors using such radiation sources. Background Art

[0002] When implementing appropriate sensors in mobile devices, home automation such as smart homes, and the automotive sector, sensing environmental parameters in the surrounding atmosphere (such as noise, sound, temperature, and gas) is becoming increasingly important. Due to air pollution and malfunctions of certain devices, harmful gas concentrations may occur. Air quality has a significant impact on health. A future theme is gas detection by inexpensive, always available, connected sensors. However, with the increasing use of sensors, there is also a particular need to be able to produce such sensors as cheaply as possible and thus cost-effectively. However, the resulting reliability and accuracy of the sensors should still be maintained or even improved.

[0003] In particular, the field of monitoring the air quality in our environment is gaining increasing attention.A typical optical sensor (e.g., a photoacoustic sensor) comprises a radiation source, a filter element for wavelength selection, a detector, and a sample region where the light between the light source and the detector interacts with the ambient medium.

[0004] Generally, there is a need in the art for a way to realize an improved radiation source for gas sensors, such as PAS sensors (PAS=Photoacoustic Spectroscopy), such that the manufacturing requirements are reduced and sufficient sensitivity is provided for the target gas to be detected by the sensor device.

[0005] This requirement can be solved by the gas sensor of the present application.

[0006] Furthermore, the specific implementation of the radiation source is defined in this application. Summary of the Invention

[0007] According to an embodiment, a radiation source for obliquely emitting narrowband electromagnetic radiation into a cavity comprises: an emitter structure having a main radiation emission area for emitting the narrowband electromagnetic radiation, wherein the emitter structure is optically coupled to the cavity; and a layer element coupled to the main radiation emission area of the emitter structure, wherein the layer element comprises a radiation deflection structure configured for deflecting a radiation emission characteristic of the emitter structure relative to a surface normal of the main radiation emission area of the emitter structure.

[0008] According to another embodiment, a radiation source for obliquely emitting narrowband IR radiation comprises: an IR emitter structure having a main radiation emitting area for emitting narrowband IR radiation; and a layer element coupled to the main radiation emitting area of the IR emitter structure, wherein the layer element comprises an IR radiation deflecting structure arranged for deflecting the IR radiation emission characteristics of the IR emitter structure relative to a surface normal of the main radiation emitting area of the IR emitter structure.

[0009] According to another embodiment, a gas sensor includes: a radiation source for obliquely emitting narrowband electromagnetic radiation into a cavity; or a radiation source for obliquely emitting narrowband IR radiation, wherein the cavity is arranged to provide an optical interaction path for causing the narrowband electromagnetic radiation having a central wavelength λ0 to interact with a target gas in the cavity, wherein the cavity is accessible to an ambient gas including a target gas component; and a radiation detector arranged to provide a detector output signal based on a signal intensity of the narrowband electromagnetic radiation that has passed through the optical interaction path and the cavity and is received by the radiation detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings, in which

[0011] Figure 1a to Figure 1b shows a schematic cross-sectional view of an IR radiation source according to an embodiment;

[0012] Figure 1c shows a resulting radiation emission characteristic of a radiation source according to an embodiment compared to a conventional radiation emission characteristic of a conventional radiation source;

[0013] Figure 2a shows a schematic cross-sectional view of an optically directional layer of a radiation deflecting structure used as a radiation source according to an embodiment;

[0014] Figure 2b to Figure 2c shows an enlarged detail view of an optically directional layer of a radiation deflecting structure used as a radiation source according to another embodiment;

[0015] Figure 3a shows a schematic cross-sectional view of an optically directional layer of a radiation deflecting structure used as a radiation source according to another embodiment;

[0016] Figure 3b shows an enlarged detail view of an optically directional layer of a radiation deflecting structure used as a radiation source according to another embodiment;

[0017] Figure 4shows a schematic cross-sectional view of a radiation source for obliquely emitting narrowband IR radiation according to an embodiment; and

[0018] Figure 5 A schematic cross-sectional view of a gas sensor (PAS sensor) according to an embodiment is shown.

[0019] Before discussing the present embodiment in further detail using the drawings, it should be noted that in the drawings and the description, identical elements and elements having identical functions and / or identical technical or physical effects are generally provided with identical reference numerals or identified by the same names, so that the descriptions of these elements and their functions as described in different embodiments can be interchanged or can be applied to each other in different embodiments. DETAILED DESCRIPTION

[0020] In the following description, various embodiments are discussed, however, it should be appreciated that each embodiment provides many applicable concepts that can be embodied in a wide variety of semiconductor devices. The specific embodiments discussed are merely illustrative of specific ways to manufacture and use the present concepts and do not limit the scope of the embodiments. In the description of the following embodiments, identical or similar elements having the same function are associated with the same reference numerals or the same names, and the description of these elements will not be repeated for each embodiment. Furthermore, unless otherwise specifically noted, the features of the different embodiments described below may be combined with each other.

[0021] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. Conversely, when an element is referred to as being "directly" connected to another element, the "connection" or "coupling" is not present in the presence of intervening elements. Other terms used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," and "on" versus "directly on," etc.).

[0022] To facilitate the description of various embodiments, the accompanying drawings include a Cartesian coordinate system x, y, z, wherein the xy plane corresponds to (i.e., is parallel to) the first main surface region of the substrate, and wherein a depth direction perpendicular to the first main surface region and into the semiconductor substrate corresponds to the "-z" direction, i.e., is parallel to the z-direction. In the following description, the term "lateral" refers to a direction parallel to the x-direction and / or the y-direction, wherein the term "vertical" refers to a direction parallel to the z-direction.

[0023] Figure 1a A radiation source 10 for obliquely emitting narrowband electromagnetic radiation 11 into a cavity 12 is shown according to an embodiment. Figure 1a , the drawing plane is parallel to the xz plane.

[0024] According to an embodiment, the radiation source 10 includes an emitter structure 14 and a layer element 18. The emitter structure 14 has a main radiation emitting region 14-1 for emitting narrowband electromagnetic radiation 11, wherein the emitter structure 14 is optically coupled to the cavity 12. The layer element 18 is coupled to the main radiation emitting region 14-1 of the emitter structure 14, wherein the layer element 18 includes a radiation deflecting (distorting) structure 20 that is configured to deflect or tilt a radiation emitting characteristic 14-A of the emitter structure 14 relative to a surface normal N of the main radiation emitting region 14-1 of the emitter structure 14.

[0025] When compared to, for example, the conventional circular radiation emission characteristics of conventional radiation sources (see, for example, Figure 1c The term "deflecting" the radiation emission characteristic of the emitter structure may also include distorting, misaligning, and / or deforming the radiation emission characteristic 14-A of the emitter structure when compared to the dotted line in FIG. A conventional circular radiation emission characteristic 14-B of a conventional radiation source may include a main radiation direction that is, for example, parallel to a surface normal of a main radiation area of such a conventional radiation source.

[0026] In a case where the radiation emission characteristics of the emitter structure 14 are already deflected relative to the surface normal of the main radiation emission area 14-1 of the emitter structure 14, the radiation deflection (=distortion) structure 20 is configured to further deflect or distort (for example, additionally tilt) the radiation emission characteristics of the emitter structure 14 relative to the surface normal of the main radiation emission area 14-1 of the emitter structure 14.

[0027] The radiation deflecting structure 20 is thus configured to modify the main radiation emission direction 14-A or the radiation emission distribution of the emitter structure 14, wherein a surface normal N of a main radiation emission area 14-1 of the emitter structure 14 may be regarded as a reference direction for describing the radiation emission characteristics of the emitter structure 14. Thus, the radiation emission characteristics of the emitter structure 14 are modified relative to the surface normal of the main radiation emission area 14-1 or relative to another reference direction with respect to the main radiation emission area 14-1 of the emitter structure 14, i.e. in the sense of a deflection, distortion, misalignment and / or deformation.

[0028] According to an embodiment, a cavity 12 into which narrowband electromagnetic radiation 11 is emitted provides an optical interaction path 15 for the narrowband electromagnetic radiation 11 having a central wavelength λ0 to interact with a target gas 17 in the cavity 12, wherein the cavity 12 may be accessible to an ambient gas or ambient gas mixture including a target gas component. In the interaction region, the target gas component absorbs the IR radiation 11 having a central wavelength λ0 if the IR radiation 11 having a central wavelength λ0 falls within the absorption spectrum of the target gas component. The degree of absorption depends on the concentration of the target gas component in the ambient gas, or is a measure of the concentration.

[0029] More specifically, measuring the intermittent or periodic absorption of the target gas inside the cavity 12 and the associated thermal heating and cooling can produce an alternating increase and decrease in the gas pressure (= pneumatic pressure) inside the cavity 12. This pressure change or variation can be detected by an acoustic transducer (e.g. a pressure-sensitive transducer, such as a MEMS microphone). The amount of absorption of the emitted thermal radiation by the gas and the associated pressure change within the cavity 12 can depend on the type of gas inside the cavity and can vary with the respective target gas and its concentration. Each target gas can include a characteristic absorption spectrum, i.e. it can cause characteristic pressure changes in response to the intermittently emitted thermal radiation. The characteristic absorption spectrum can also be referred to as a gas-specific fingerprint. Thus, an acoustic transducer (e.g. see Figure 5 ) can record signals that may be characteristic of the corresponding target gas, so that the acoustic transducer can thereby detect and identify the corresponding target gas and its concentration.

[0030] like Figure 1a As shown, the cavity 12 is formed by an inner wall element 16-1 of the housing 16, wherein the layer element 18 includes a radiation deflecting structure 20 for deflecting a radiation emission characteristic of the emitter structure 14 relative to the inner wall element 16-1, which faces a main radiation emitting area 14-1 of the emitter structure 14. The inner wall element 16-1 may include a flat surface, wherein a surface normal of the inner wall element 16-1 and the main radiation emitting area 14-1 of the emitter structure 14 may be arranged parallel or substantially parallel to each other.

[0031] The cavity 12 may be a substantially closed cavity surrounding the emitter structure 14 having the layer element 18, wherein the cavity 12 may include at least one inlet opening 32 through which ambient gas (e.g., ambient air) may flow into the cavity. The cavity 12 may be formed by an inner wall element of the housing.

[0032] like Figure 1a As shown in the example, the thickness is d 18The optical directional layer 18 may be arranged for providing a (relatively) parallel deflection or tilting of the emitted radiation 11 along the diameter D of the layer element 18 .

[0033] Figure 1b A further radiation source 10 for obliquely emitting narrowband electromagnetic radiation 11 into a cavity 12 according to a further embodiment is shown. Figure 1b The function and structure of the radiation source 10 are similar to Figure 1a The function and structure of the radiation source 10 are essentially the same, wherein the optical directional layer 18 may also be arranged for providing a variation or change in the deflection of the emitted radiation 11 along the diameter D of the layer element 18 .

[0034] Figure 1c The resulting radiation emission characteristic 14-A of the radiation source 14 according to the embodiment is shown in comparison with a conventional radiation emission characteristic of a conventional radiation source. The conventional radiation emission characteristic is shown in dashed lines. Figure 1c , an optical intensity pattern according to a radiation emission profile of a radiation source is plotted parallel to the xy plane.

[0035] like Figure 1c As shown, the radiation emission characteristics of the conventional emitter structure are generally circular and centered relative to the main radiation emission area of the conventional emitter (see Figure 1c Because the optical radiation is circular and centered relative to the light source, a substantial portion of the emitted radiation strikes the cavity wall facing the emitter perpendicularly or nearly perpendicularly. Consequently, a substantial portion of the emitted radiation may be reflected back toward a conventional emitter, for example, due to the parallel or coplanar nature of the cavity walls.

[0036] like Figure 1c As further shown, the adjusted radiation emission characteristic of the emitter structure according to an embodiment is deflected, for example, misaligned and / or deformed, relative to the surface normal N of the main radiation emission region 14-1 of the emitter structure according to an embodiment. Because the optical radiation 11 is deflected relative to the surface normal of the main radiation emission region 14-1 of the emitter structure 14, a substantial portion or a major portion of the emitted radiation strikes the cavity wall facing the emitter at an acute angle α (e.g., at an impact angle between 10° and 70° or between 20° and 60°) and is thus reflected. As a result, a substantial portion of the emitted radiation can be reflected multiple times at different cavity walls, and a significant interaction length 15 (=optical path length in the target gas component) with the target gas component can be achieved in the cavity 12. This is particularly true if the cavity 12 is formed as a waveguide or reflective housing, in which a reflective coating, such as a metal layer on a shaped structural housing wall (=cavity wall) 16-1, guides the emitted radiation 11 through the interaction path by means of reflection.

[0037] According to an embodiment, the main radiation emitting region 14-1 of the emitter structure 14 is configured for emitting narrowband electromagnetic radiation 11. Thus, the emitter structure 14 may be configured to emit electromagnetic radiation (e.g., thermal radiation) in a specific wavelength spectrum into the cavity 12. The wavelength of the emitted narrowband electromagnetic (e.g., thermal) radiation may depend on the gas to be detected, i.e., the target gas in the ambient atmosphere. For example, the target gas may include carbon monoxide CO, carbon dioxide CO2, ozone O3, nitrogen oxides NO x , methane CH4, etc. However, this list of target gases to be detected should not be considered an exhaustive list.

[0038] According to an embodiment, the emitter structure 14 may be configured to emit narrowband electromagnetic radiation intermittently or periodically. The emitter structure 14 may also include a heat source and / or an infrared source, and optionally a wavelength selective structure 30, which is configured to provide the narrowband electromagnetic radiation 11. As a result, the ambient gas inside the cavity 12 (including the target gas) absorbs the emitted electromagnetic radiation 11, wherein such absorption by the gas may result in an increase in temperature and, therefore, an increase in pressure inside the cavity 12. For example, this alternating change in pressure may be detected by an acoustic transducer ( Figure 1a to Figure 1b The amount of target gas absorption of the emitted thermal radiation and the associated pressure change within cavity 12 may depend on the type and amount of target gas within cavity 12 and may vary with the target gas. An emitter structure 14 is optically coupled to cavity 12.

[0039] In this specification, infrared radiation (IR) is mentioned as a non-limiting example of thermal radiation. Thermal radiation can be any radiation above absolute zero starting from 0° Kelvin. In general, infrared radiation can be a specific part of thermal radiation. Additionally, radiation sources are mentioned and can include infrared radiation sources, light emitting diodes (LEDs), laser sources, or thermal sources.

[0040] According to an embodiment, Figure 1a to Figure 1b The thickness d of the layer element 18 18 Typical dimensions of the layer element 18 may range between 100 nm and a few micrometers (eg 2 μm, 3 μm or 4 μm). If the dimension of the layer element 18 (=thickness d 18 ) up to or including an integer multiple of one quarter of the wavelength of the radiation R (e.g. half the wavelength or one quarter of the wavelength of the IR radiation emitted by the emitter structure 14), the layer element 18 itself can act as a filter, for example as a plasmonic structure in a plane parallel to the z direction and / or as a Bragg filter parallel to the x / y plane. Thus, the layer element 18 itself can provide the functionality of an optional wavelength selective structure (IR filter) 30, for example for providing narrowband electromagnetic radiation 11.

[0041] Figure 2a shows a schematic cross-sectional view of an optically directional layer 18 according to an embodiment, the optically directional layer 18 being used as a radiation source 10 with a thickness d 18 The radiation deflection structure 18. Figures 2a to 2c , the drawing plane is parallel to the xz plane.

[0042] According to an embodiment, the radiation deflecting structure 20 of the layer element 18 comprises a plurality of light guiding elements or light channels 22 , wherein the orientation of the light guiding elements 22 is angularly offset by an angle β relative to a surface normal N of the main radiation emission region 14 - 1 of the emitter structure 14 .

[0043] like Figure 2a As shown, the wider angular range I describes the maximum optical transmission range of the light channel 22 , wherein the narrower angular range II describes the resulting deflection angle of the light channel 22 of the radiation deflecting structure 20 .

[0044] Figure 2b to Figure 2c An enlarged detail view of an optically directional layer according to another embodiment is shown, which is used as a radiation-distorting structure of a radiation source.

[0045] like Figure 2b As shown, the light guiding element 22 may be formed as angled transparent channels 23 separated by optically opaque or reflective interlayers 24, wherein the transparent channels 23 and the optically opaque or reflective interlayers 24 are arranged in an alternating and adjacent configuration.

[0046] like Figure 2c As shown, the light guide element 22 may include transparent regions 23 and opaque or reflective wall regions 25 , wherein the transparent regions 23 and the opaque or reflective wall regions 25 are arranged in an alternating and adjacent configuration.

[0047] according to Figures 2a to 2c In an embodiment, the transparent region 23 may include, for example, glass, silicon oxide, silicon dioxide, polysilicon, silicon nitride, carbon, and / or pyrex as a transparent material. The opaque or reflective wall regions 24, 25 may include, for example, common metals (e.g., aluminum, gold, platinum, etc.), plastics, plastic compounds, carbon, and / or molded materials as opaque or reflective materials. Furthermore, if the transparent materials are properly aligned to have total reflection, they can be used for reflective interfaces.

[0048] Figure 3a A thickness d according to another embodiment is shown. 18 Schematic cross-sectional view of an optically directional layer 18 used as a radiation-distorting structure 20 of a radiation source 10. Figure 3a to Figure 3b , the drawing plane is parallel to the xz plane.

[0049] like Figure 3a As shown, the layer element 18 may include a plurality of structured sublayers 18-1, ..., 18-n arranged to provide an angularly offset light guiding element 22, wherein the sublayers 18-1, ..., 18-n extend parallel to the surface of the main radiation emitting region 14-1 of the emitter structure 14. Figure 3a As shown exemplarily, the layer element 18 may comprise three structured sub-layers 18-1, 18-2, 18-3. However, the number n of sub-layers 18-n may depend on the respective thicknesses of the sub-layers and the desired thickness d of the resulting layer element 18. 18 , the required thickness d 18 For providing the desired channel length and channel angle relative to the surface normal N of the main radiation emission region 14-1 of the emitter structure 14. By forming the layer element 18 using a plurality of structured sublayers 18-1, ..., 18-n, precise repeatability of the tilted light guiding element 22 can be achieved.

[0050] like Figure 3a As shown, the wider angular range I describes the maximum optical transmission range of the light channel 22 , wherein the narrower angular range II describes the resulting deflection angle of the light channel 22 of the radiation deflecting structure 20 .

[0051] Figure 3b An enlarged detail view of an optical directional layer 18 according to another embodiment is shown, which is used as a radiation-distorting structure 20 of a radiation source 10. Light-guiding element 22 includes transparent regions 23-1, ..., 23-n and opaque or reflective wall regions 24-1, ..., 24-n, 25-1, ..., 25-n, wherein transparent regions 23-1, ..., 23-2 and opaque or reflective wall regions 24-1, ..., 24-n, 25-1, ..., 25-n are arranged in an alternating and adjacent configuration in structured sublayers 18-1, 18-2, 18-3. Transparent regions 23-n can include, for example, glass, silicon oxide, silicon dioxide, polycrystalline silicon, silicon nitride, carbon, and / or pyrex as the transparent material. The opaque wall areas or reflective wall areas 24-1, ..., 24-n (=24), 25-1, ..., 25-n (=25) can include, for example, general metals (e.g., aluminum, gold, platinum, etc.), plastics, plastic compounds, carbon and / or molded materials as opaque materials or reflective materials. In addition, if transparent materials are properly aligned to have total reflection, they can be used for reflective interfaces.

[0052] like Figures 2a to 2c and Figure 3a to Figure 3bAs exemplarily shown, the light-guiding elements 22 of the optical directional layer 18 are arranged in a parallel orientation or direction relative to each other for providing a (relatively) parallel deflection or tilt of the emitted radiation 11 (see, for example, FIG. Figure 1a ).

[0053] Thus, the radiation deflecting structure 20 in the layer element 18 can be arranged to provide a (relatively) constant and / or identical deflection angle (= deflection) β of the emitted radiation 11 along the diameter D of the layer element 18 (and towards the edge), which results in a (relatively) parallel deflection or tilt of the emitted radiation 11 relative to the surface normal of the main surface area 18-A of the layer element 18 along its diameter D. This parallel deflection of the emitted radiation 11 can be achieved, for example, by means of a light-guiding element 22 of the radiation deflecting structure 20 in the layer element 18 (see Figures 2a to 2c and Figure 3a to Figure 3b ) is achieved by a parallel orientation of the light guide elements 22. Thus, the light guide elements 22 are arranged in a parallel orientation or direction relative to each other.

[0054] According to another embodiment, the light guiding elements 22 of the optical directional layer 18 may also be arranged in different orientations or directions relative to each other for providing a variation of the deflection of the emitted radiation 11 (see, for example, Figure 1b ).according to Figure 1b In the case of a radiation source 10 for obliquely emitting narrowband electromagnetic radiation 11 into a cavity 12, the optically directional layer (= layer element) 18 may be arranged to provide a changing or different deflection angle (= deflection) β of the emitted radiation 11 along the diameter D of the layer element 18 (and towards the edge), which results in a changing or different deflection or tilt of the emitted radiation 11 relative to the surface normal of the main surface area 18-A of the layer element 18 along the diameter D. As described above Figure 1b As shown, the layer elements 18 can be arranged to provide an increased deflection angle (=deflection) β of the emitted radiation 11 along the diameter D.

[0055] Such a change in the deflection of the emitted radiation 11 can be achieved, for example, by varying (gradually increasing or decreasing) the deflection angle β (=deflection) and / or the orientation of the light-guiding elements 22 of the radiation-deflecting structures 20 in the layer element 18. Such a change in the deflection of the emitted radiation 11 can also be achieved, for example, by a segmented change in the orientation of the light-guiding elements 22 of the radiation-deflecting structures 20 in the layer element 18, for example, in groups of light-guiding elements 22. Thus, the light-guiding elements 22 can be arranged in different orientations or directions relative to one another.

[0056] According to an embodiment, the emitter structure 14 may include an LED element, a laser element and / or an infrared source (=heat source). According to another embodiment, the emitter structure 14 may include an infrared source and a wavelength selective structure 30 configured for providing narrowband electromagnetic radiation 11 .

[0057] With reference to all the embodiments described above, the radiation source 10 for obliquely emitting narrowband electromagnetic radiation 11 into the cavity 12 is implemented by attaching an optical interface formed by a layer element 18 to the optical window 14-1 of the light / radiation source 10 (i.e., to the main radiation emission area 14-1 of the emitter structure 14). The optical interface 18 modifies the directivity pattern, i.e., the radiation emission characteristics of the emitter structure 14 with respect to light intensity and package geometry, to optimize the illumination of the volume in the cavity 12 (i.e., the interaction area).

[0058] According to various embodiments, one layer or a stack of multiple layers 18 may serve as a waveguide for light (=radiation) launched into a cavity 12 , eg a PAS cavity (PAS=photoacoustic spectroscopy), to increase the absorption distance of the radiation 11 in the cavity 12 .

[0059] The described embodiment of radiation source 10 can be realized by maintaining the mounting principle of an SMD or similar simple standards, wherein the optical radiation direction can be adjusted by means of optical directional layer 18 .

[0060] According to an embodiment, the optical directional layer (= layer element) 18 can be realized as a lateral layer, which is constructed to waveguide and / or reflect the outgoing light (= radiation) 11 and can be attached to a filter (= wavelength selection structure) and / or can be part of a filter.

[0061] According to an embodiment, the layer element 18 may comprise alternating optically transparent and optically blocking (absorbing or reflecting) slanted grooves 22, wherein the layer element 18 may be arranged perpendicular to the optical window 14-1 (=main radiation emitting area 14-1 of the emitter structure 14). The optical window 14-1 is the interface between the light source / radiation source 10 and the packaging outside the emitter structure 14.

[0062] According to an embodiment, the radiation source 10 may provide collimated light (=radiation) 11 for emission into the cavity 18 by means of the layer element 18. Furthermore, the exit light pattern may be optimized to increase the absorption paths in a given cavity 12 and to maximize the illumination of the target gas in this cavity 12.

[0063] According to an embodiment, the radiation source 10 may be a sub-part or component of a system, such as a photoacoustic spectrometer (PAS sensor) or a non-dispersive infrared (NDIR) sensor. According to another embodiment, the radiation source 10 may be applied to light radiation applications such as LEDs or light bulbs.

[0064] Various embodiments allow realizing a radiation source 10 with a small form factor, wherein also a cheap (less complex) packaging can be applied.

[0065] Figure 4 1 shows a schematic cross-sectional view of a radiation source 10 for obliquely emitting narrowband IR radiation 11 according to another embodiment. Figure 4 , the drawing plane is parallel to the xz plane.

[0066] According to an embodiment, a radiation source 10 for obliquely emitting narrowband IR radiation 11 comprises an IR emitter structure 14 having a main radiation emitting area 14-1 for emitting the narrowband IR radiation 11, and a layer element 18 coupled to the main radiation emitting area 14-A of the IR emitter structure 14. The layer element 18 comprises an IR radiation deflecting structure 20 arranged for deflecting an IR radiation emission characteristic of the IR emitter structure 14 relative to a surface normal of the main radiation emitting area 14-A of the IR emitter structure 14.

[0067] Combination with thermal (=IR) radiation source 10 Figures 1a to 3b The above assessment also applies to Figure 4 Radiation source 10.

[0068] According to an embodiment, the IR emitter structure 14 can be formed as a thermal emitter (=IR source) that includes a freestanding film 14-2 supported by a substrate 14-3, wherein the freestanding film 14-2 includes a conductive segment 14-4 that can be arranged on or embedded in the freestanding film 14-2. The conductive segment 14-4 can include a conductive semiconductor material that forms a current path for the thermal emitter. The conductive segment 14-4 of the freestanding film 14-2 can include a heavily doped semiconductor layer that can include polycrystalline silicon or single crystal silicon. The conductive segment 14-4 of the freestanding film 14-2 can be arranged over a cavity 14-5 in the substrate 14-3, wherein the freestanding film 14-2 can cover the cavity 14-5 in the substrate 14-3. The substrate 14 - 3 may include a bulk semiconductor substrate and an insulating layer 14 - 6 , wherein the insulating layer 14 - 6 forms a major surface region 14 -A of the substrate 14 - 3 to which the freestanding film 14 - 2 is attached.

[0069] Furthermore, the membrane 14-2 may include a vertical thickness or height that is substantially smaller than the lateral extension of the membrane 14-2. The thickness of certain elements (e.g., the thickness of the membrane structure, semiconductor substrate, heating structure, heating element, and gas absorber layer) may not be drawn to scale.

[0070] According to an embodiment, the IR emitter structure 14 may comprise a wavelength selective structure (IR filter) 30 configured to provide narrowband IR radiation 11 with a central wavelength λ0, which for example falls within the absorption spectrum of a target gas component.

[0071] The wavelength selective structure 30 can be formed as an IR filter, for example, with an FP filter stack (=Bragg reflector) or a Fabry-Perot filter element with a first Fabry-Perot filter stack 30-1 and a second Fabry-Perot filter stack 30-2, which are arranged in a relative face-to-face configuration with an interposed dielectric layer 30-3.

[0072] The wavelength selective structure 30 may also include a plasmonic structure on the freestanding film 14-2, wherein the plasmonic structure forms a bandpass filter for IR radiation emitted by the freestanding film during operation of the thermal emitter structure 14. The plasmonic structure 30 may form a plasmonic resonator for the emitted IR radiation.

[0073] According to an embodiment, the thermal emitter structure 10 is formed as a MEMSIR emitter having an operating temperature between 800°C and 1100°C.

[0074] According to an embodiment, the IR radiation source 10 may be arranged for emitting narrowband IR radiation 11 obliquely into the cavity 12 ( Figure 4 ), wherein the IR emitter structure 14 can be coupled to a housing 16 having an inner wall element ( Figure 4 ), the inner wall element at least partially forming the cavity 12 and wherein the IR radiation deflecting structure 20 may be arranged for deflecting the IR radiation emission characteristics of the IR emitter structure 14 relative to the wall element facing the main radiation emitting area 14-A of the IR emitter structure 14.

[0075] According to an embodiment, the radiation deflecting structure 20 of the layer element 18 comprises a plurality of light guiding elements 22 between opposite main surface areas 18 - 1 of the layer element 18 , wherein the orientation of the light guiding elements 22 is angularly offset relative to the surface normal of the main radiation emitting area 14 -A of the IR emitter structure 14 .

[0076] According to an embodiment, the light guiding element 22 is formed as inclined transparent channels separated by optically opaque or reflective intermediate layers, wherein the transparent channels 22 - 1 and the optically opaque or reflective intermediate layers 22 - 2 are arranged in an alternating and adjacent configuration.

[0077] According to an embodiment, the layer element 18 may include a plurality of structured sublayers 26 arranged for providing an angularly offset light guiding element 22 , wherein the sublayers extend parallel to the main radiation emitting area 14 -A of the IR emitter structure 14 .

[0078] Figure 5 1 shows a schematic cross-sectional view of a gas sensor (eg, a PAS sensor) 100 according to an embodiment. Figure 5 , the drawing plane is parallel to the xz plane.

[0079] The gas sensor 100 comprises a radiation source 10 according to any of the embodiments described above for obliquely emitting narrowband electromagnetic radiation 11 into a cavity 12 and / or for obliquely emitting narrowband IR radiation 11 .

[0080] Combinations related to radiation source 10 Figure 1a to Figure 1b 、 Figures 2a to 2c 、 Figure 3a to Figure 3b and Figure 4 The above assessment also applies to Figure 5 Radiation source 10.

[0081] The cavity 12 is arranged to provide an optical interaction path for narrowband electromagnetic radiation 11 having a central wavelength λ0 to interact with a target gas in the cavity 12 , wherein the cavity 12 is accessible to an ambient gas comprising a target gas component, eg via an access opening 32 .

[0082] The gas sensor further comprises a radiation detector 34 arranged to provide a detector output signal based on the signal strength of the narrowband electromagnetic radiation 11 that has passed through the optical interaction path and the cavity 12 and is received by the radiation detector.

[0083] Therefore, the gas sensor 100 can be formed as a MEMS gas sensor (MEMS = micro-electromechanical system), which includes a photoacoustic sensor 34 having a thermal emitter 10 according to any of the aforementioned embodiments, and an acoustic transducer 34 (e.g., a MEMS microphone), wherein the thermal emitter 10 and the acoustic transducer 34 are arranged inside a mutual measurement cavity 12.

[0084] As described with respect to the previous embodiments, the adjusted radiation emission characteristic 14-A of the emitter structure 14 is deflected, e.g., misaligned and / or distorted, relative to the surface normal N of the main radiation emission area 14-1 of the emitter structure 14. Because the optical radiation 11 is deflected relative to the surface normal N of the main radiation emission area 14-1 of the emitter structure 14, a substantial portion or a major portion of the emitted radiation 11 strikes the cavity wall 16-1 facing the emitter at an acute angle α (e.g., an impact angle between 10° and 70° or 20° and 60°) and is thus reflected. As a result, a substantial portion of the emitted radiation 11 can be reflected multiple times at different cavity walls 16-1 and a significant interaction length 15 (=optical path length in the target gas component) with the target gas component can be achieved in the cavity 12. Because the cavity 12 can be formed as a waveguide or reflective housing 36, a reflective coating, such as a metal layer on the shaped structural housing wall 16-1 (=cavity wall), can guide the emitted radiation through the interaction path by means of reflection.

[0085] like Figure 5 As shown, the cavity 12 is formed by an inner wall element 16-1 of the housing 16, wherein the layer element 18 includes a radiation deflecting structure 20 for deflecting a radiation emission characteristic of the emitter structure 14 relative to the inner wall element 16-1 facing the main radiation emitting area 14-A of the emitter structure 14. The inner wall element 16-1 may include a planar surface, wherein the surface normal of the inner wall element 16-1 and the surface normal of the main radiation emitting area 14-A of the emitter structure 14 may be arranged to be parallel or substantially parallel to each other. The cavity 12 may be a substantially closed cavity surrounding the emitter structure 14 having the layer element 18, wherein the cavity 12 may include at least one inlet opening 32 through which ambient gas (e.g., ambient air) may flow into the cavity. The cavity 12 may be formed by the inner wall element of the housing.

[0086] The specific wavelength of the emitted radiation 11 can be set to the corresponding gas or gas component to be detected, i.e., the so-called analysis gas or target gas. The emitter structure 14 can be configured to emit thermal radiation 11 intermittently or periodically. Consequently, the ambient gas (including the target gas) within the measurement cavity 12 absorbs the intermittently emitted thermal radiation, causing the gas to intermittently or periodically heat and cool in response to the emitted thermal radiation. Because a substantial portion of the emitted radiation may be reflected multiple times at different cavity walls and may achieve a significant interaction length (= optical path length in the target gas component) with the target gas component in cavity 12, this absorption and associated heating and cooling of the gas within the measurement cavity 12 can result in alternating increases and decreases in pressure within the cavity 12. These pressure changes can be detected by an acoustic transducer (e.g., a MEMS microphone). The amount of gas absorption of the emitted thermal radiation and the associated pressure changes within the cavity 12 can depend on the type of gas within the cavity and can vary with the target gas and its concentration. Each target gas may have a characteristic absorption spectrum, i.e., it may induce a characteristic pressure change in response to the emitted thermal radiation. This characteristic absorption spectrum may also be referred to as a gas-specific fingerprint. Thus, the acoustic transducer may record a signal that may be characteristic of the corresponding target gas, thereby enabling the acoustic transducer to detect and identify the corresponding target gas.

[0087] Other embodiments and aspects are described that may be used alone or in combination with the features and functionality described herein.

[0088] According to an embodiment, a radiation source for obliquely emitting narrowband electromagnetic radiation into a cavity comprises: an emitter structure having a main radiation emission area for emitting the narrowband electromagnetic radiation, wherein the emitter structure is optically coupled to the cavity; and a layer element coupled to the main radiation emission area of the emitter structure, wherein the layer element comprises a radiation deflecting or distortion structure configured for deflecting a radiation emission characteristic of the emitter structure relative to a surface normal of the main radiation emission area of the emitter structure.

[0089] According to an embodiment, the cavity is formed by an inner wall element of the housing, wherein the layer element comprises a radiation deflecting structure for deflecting a radiation emission characteristic of the emitter structure relative to the inner wall element, which inner wall element faces a main radiation emission area of the emitter structure.

[0090] According to an embodiment, the radiation deflecting structure of the layer element comprises a plurality of light guiding elements, wherein the orientation of the light guiding elements is angularly offset with respect to a surface normal of a main radiation emission region of the emitter structure.

[0091] According to an embodiment, the light guiding elements are formed as inclined transparent channels separated by optically opaque or reflective intermediate layers, wherein the transparent channels and the optically opaque or reflective intermediate layers are arranged in an alternating and adjacent configuration.

[0092] According to an embodiment, the light guiding element comprises transparent areas and opaque wall areas or reflective wall areas, wherein the transparent areas and the opaque wall areas or reflective wall areas are arranged in an alternating and adjacent configuration.

[0093] According to an embodiment, the layer element comprises a plurality of structured sublayers arranged for providing an angularly offset light guiding element, wherein the sublayers extend parallel to a main radiation emission area of the emitter structure.

[0094] According to an embodiment, the light guiding elements are arranged in a parallel orientation relative to each other.

[0095] According to an embodiment, the light guiding elements comprise different orientations relative to each other.

[0096] According to an embodiment, the emitter structure comprises an LED element, a laser element and / or an infrared source.

[0097] According to an embodiment, an emitter structure comprises an infrared source and a wavelength selective structure configured for providing narrowband electromagnetic radiation.

[0098] According to an embodiment, a radiation source for obliquely emitting narrowband IR radiation comprises: an IR emitter structure having a main radiation emitting area for emitting narrowband IR radiation; and a layer element coupled to the main radiation emitting area of the IR emitter structure, wherein the layer element comprises an IR radiation deflecting structure arranged for deflecting the IR radiation emission characteristics of the IR emitter structure relative to a surface normal of the main radiation emitting area of the IR emitter structure.

[0099] According to an embodiment, the IR radiation source is arranged for emitting narrowband IR radiation obliquely into the cavity, wherein the IR emitter structure is coupled to a housing having an inner wall element which at least partially forms the cavity, and wherein the IR radiation deflecting structure is arranged for deflecting the IR radiation emission characteristic of the IR emitter structure relative to the wall element, which wall element faces a main radiation emission area of the IR emitter structure.

[0100] According to an embodiment, the radiation deflecting structure of the layer element comprises a plurality of light guiding elements between opposite main surface areas of the layer element, wherein the orientation of the light guiding elements is angularly offset with respect to a surface normal of a main radiation emitting area of the IR emitter structure.

[0101] According to an embodiment, the light guiding elements are formed as inclined transparent channels separated by optically opaque or reflective intermediate layers, wherein the transparent channels and the optically opaque or reflective intermediate layers are arranged in an alternating and adjacent configuration.

[0102] According to an embodiment, the layer element comprises a plurality of structured sublayers arranged for providing an angularly offset light guiding element, wherein the sublayers extend parallel to a main radiation emitting area of the IR emitter structure.

[0103] According to an embodiment, an IR emitter structure includes an infrared source and a wavelength selective structure configured for providing narrowband IR radiation.

[0104] According to an embodiment, the thickness of the layer element comprises an integer multiple of one quarter of the wavelength of the IR radiation emitted by the emitter structure.

[0105] According to an embodiment, a gas sensor comprises: a radiation source according to any one of the aforementioned embodiments, for obliquely emitting narrowband electromagnetic radiation into a cavity, wherein the cavity is arranged to provide an optical interaction path for causing the narrowband electromagnetic radiation having a central wavelength to interact with a target gas in the cavity, wherein the cavity is accessible to an ambient gas including a target gas component; and a radiation detector, which is arranged to provide a detector output signal based on a signal intensity of the narrowband electromagnetic radiation that has passed through the optical interaction path and the cavity and is received by the radiation detector.

[0106] Although some aspects have been described as features in the context of an apparatus, it is obvious that such description can also be considered as a description of corresponding features of a method. Although some aspects have been described as features in the context of a method, it is obvious that such description can also be considered as a description of corresponding features with respect to the functionality of the apparatus.

[0107] In the foregoing detailed description, it can be seen that in order to simplify the present disclosure, various features are grouped together in the various examples. The method of the present disclosure should not be interpreted as reflecting the following intention: the examples required for protection require more features than the features explicitly stated in each claim. On the contrary, as reflected in the following claims, the subject matter may lie in features that are less than all the features of a single disclosed embodiment. Therefore, the following claims are hereby incorporated into the detailed description, wherein each claim can exist independently as a separate example. Although each claim can stand alone as a separate example, it should be noted that although a dependent claim can refer to a specific combination with one or more other claims in a claim, other examples can also include a combination of a dependent claim with the subject matter of each other dependent claim, or a combination of each feature with other dependent claims or independent claims. Unless it is indicated that a specific combination is not intended, such a combination is proposed herein. Furthermore, it is intended that even if a claim is not directly subordinate to an independent claim, the features of the claim will be included in any other independent claim.

[0108] Although specific embodiments have been illustrated and described herein, it will be appreciated by those skilled in the art that various alternative implementations and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present embodiments. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. It is therefore intended that the embodiments be limited only by the claims and their equivalents.

Claims

1. A radiation source (10) for obliquely emitting narrowband electromagnetic radiation (11) into a cavity (12), comprising: an emitter structure (14) having a main radiation emitting region (14-1) for emitting the narrowband electromagnetic radiation (11), wherein the emitter structure (14) is optically coupled to the cavity (12); as well as a layer element (18) coupled to the main radiation emitting region (14-1) of the emitter structure (14), wherein the layer element (18) comprises a radiation deflecting structure (20) configured to deflect a radiation emission characteristic of the emitter structure (14) relative to a surface normal (N) of the main radiation emitting region (14-1) of the emitter structure (14), wherein the radiation deflecting structure (20) of the layer element (18) comprises a plurality of light-guiding elements (22), wherein the orientation of the light-guiding elements (22) is angularly offset with respect to a surface normal of the main radiation emission area (14-1) of the emitter structure (14), wherein the light-guiding elements (22) are formed as inclined transparent channels (23) separated by optically opaque or reflective intermediate layers (24), wherein the transparent channels (23) and the optically opaque or reflective intermediate layers (24) are arranged in an alternating and adjacent configuration, and / or The light-guiding element (22) comprises transparent areas (23) and opaque wall areas or reflective wall areas (25), wherein the transparent areas (23) and the opaque wall areas or reflective wall areas (25) are arranged in an alternating and adjacent configuration.

2. The radiation source (10) according to claim 1, wherein the cavity (12) is formed by an inner wall element (16-1) of a housing (16), wherein the layer element (18) comprises the radiation deflection structure (20), the radiation deflection structure (20) being used to deflect the radiation emission characteristics of the emitter structure (14) relative to the inner wall element (16-1), the inner wall element (16-1) facing the main radiation emission area (14-1) of the emitter structure (14).

3. A radiation source (10) according to claim 1 or 2, wherein the layer element (18) comprises a plurality of structured sublayers (18-1, ..., 18-n), and the plurality of structured sublayers (18-1, ..., 18-n) are arranged to provide the light-guiding element (22) with an angle offset, wherein the sublayers (18-1, ..., 18-n) extend parallel to the main radiation emission area (14-1) of the emitter structure (14).

4. The radiation source (10) of claim 1, wherein the light-guiding elements (22) are arranged in a parallel orientation relative to each other.

5. The radiation source (10) of claim 1, wherein the light-guiding elements (22) comprise different orientations relative to each other.

6. The radiation source (10) according to claim 1 or 2, wherein the emitter structure (14) comprises an LED element, a laser element and / or an infrared source.

7. The radiation source (10) of claim 1 or 2, wherein the emitter structure (14) comprises an infrared source and a wavelength selective structure (30), the wavelength selective structure (30) being configured for providing the narrowband electromagnetic radiation (11).

8. A radiation source (10) for obliquely emitting narrowband IR radiation (11), comprising: an IR emitter structure (14) having a primary radiation emitting region (14-1) for emitting narrowband IR radiation (11); as well as a layer element (18) coupled to the main radiation emitting area (14-1) of the IR emitter structure (14), wherein the layer element (18) comprises an IR radiation deflecting structure (20) arranged for deflecting an IR radiation emission characteristic of the IR emitter structure (14) relative to a surface normal of the main radiation emitting area (14-1) of the IR emitter structure (14), wherein the radiation deflecting structure (20) of the layer element (18) comprises a plurality of light-guiding elements (22) between opposite main surface areas (18-1) of the layer element (18), wherein the orientation of the light-guiding elements (22) is angularly offset with respect to a surface normal of the main radiation emitting area (14-1) of the IR emitter structure (14), The light-guiding elements (22) are formed as inclined transparent channels separated by optically opaque or reflective intermediate layers, wherein the transparent channels (22-1) and the optically opaque or reflective intermediate layers (22-2) are arranged in an alternating and adjacent configuration.

9. The radiation source (10) of claim 8, wherein the IR radiation source (10) is arranged for emitting narrowband IR radiation (11) obliquely into a cavity (12), wherein the IR emitter structure (14) is coupled to a housing (16), the housing (16) having an inner wall element (16-1), the inner wall element (16-1) at least partially forming the cavity (12), and wherein the IR radiation deflecting structure (20) is arranged for deflecting the IR radiation emission characteristic of the IR emitter structure (14) relative to the wall element (16-1), the wall element (16-1) facing the main radiation emission area (14-1) of the IR emitter structure (14).

10. The radiation source (10) of claim 8, wherein the layer element (18) comprises a plurality of structured sublayers (26) arranged to provide the light-guiding element (22) with an angular offset, wherein the sublayers extend parallel to the main radiation emission area (14-1) of the IR emitter structure (14).

11. The radiation source (10) according to claim 8 or 9, wherein the IR emitter structure (14) comprises an infrared source and a wavelength selective structure, the wavelength selective structure being configured for providing the narrowband IR radiation (11).

12. The radiation source (10) according to claim 8 or 9, wherein the thickness (d 18 ) comprises an integer multiple of one quarter of the wavelength of the IR radiation emitted by the emitter structure (14).

13. A gas sensor (100), comprising: The radiation source (10) according to any one of the preceding claims, for obliquely emitting narrowband electromagnetic radiation (11) into the cavity (12); wherein the cavity (12) is arranged to provide an optical interaction path for the narrowband electromagnetic radiation (11) having a central wavelength λ0 to interact with a target gas in the cavity (12), wherein the cavity (12) is accessible to an ambient gas including a component of the target gas; as well as A radiation detector is arranged to provide a detector output signal based on a signal strength of the narrowband electromagnetic radiation (11) that has passed through the optical interaction path and the cavity (12) and is received by the radiation detector.

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