METAMATERIAL-BASED IR EMITTER HAVING MODULATABLE EMISSIVITY

Abstract

The invention relates to a modulatable infrared emitter comprising a heating element, a planar base element, a dielectric interlayer, and a planar cover element which is a structured metamaterial, and an actuator, wherein the actuator is configured for a relative movement of the cover element and the base element between a first and a second position in order to modulate the intensity of the emission of the infrared emitter. The invention further relates to production methods for the infrared emitter, methods for the modulated emission of infrared red radiation by means of the infrared emitter, and preferred uses of the infrared emitter. A system comprising the infrared emitter and a control device for regulating the actuator are also preferably the subject matter of the invention.

Claims

1. A modulatable infrared emitter, comprising a heating element; a planar base element made of a conductive material; a dielectric interlayer; a planar cover element made of a conductive material; and an actuator, wherein the cover element is a structured metamaterial with periodically arranged unit cells and the actuator is configured for relative movement of the cover element and the base element between a first and second position in order to modulate the intensity of the emission of the infrared emitter.

2. The modulatable infrared emitter according to claim 1, wherein the relative movement comprises a vertical translational movement of the cover element and/or base element along the emission direction of the infrared emitter, which changes the distance between the cover element and the base element.

3. The modulatable infrared emitter according to claim 1, wherein the relative movement comprises a horizontal translational movement of the cover element and/or base element orthogonal to the emission direction of the infrared emitter, which changes the degree of overlap between the cover element and the base element.

4. The modulatable infrared emitter according to claim 1, wherein the emissivity in the direction of the surface normal of the cover element for at least one resonance wavelength, in a range of from 1 μm to 10 μm, is higher in the second position than in the first position by a factor of 2.

5. The modulatable infrared emitter according to claim 2, wherein the emissivity in the direction of the surface normal of the cover element for at least one resonance wavelength, in a range of from 1 μm to 10 μm, has a value of more than 0.7, in the second position and a value of less than 0.4 in the first position.

6. The modulatable infrared emitter according to claim 1, wherein the unit cell comprises a resonator which is formed by bracing the conductive material, wherein the resonator preferably has the shape of a split ring resonator (SRR), an electric ring resonator (ERR), a cross, a square, a circle, a hexagon, and/or combinations of these shapes.

7. The modulatable infrared emitter according to claim 1, wherein the unit cells form a two-dimensional periodic lattice, wherein the lattice angle is between 60° and 120° and the two lattice constants are between 5% and 40% of a resonance wavelength.

8. The modulatable infrared emitter according any to claim 1, wherein the cover element is made from a metal and/or wherein the dielectric interlayer is made of a material selected from a group comprising aluminum nitride, silicon nitride, aluminum oxide, silicon oxide, titanium dioxide, and/or tantalum oxide.

9. (canceled)

10. (canceled)

11. The modulatable infrared emitter according to claim 1, wherein the cover element, the dielectric interlayer, and/or the base element have a layer thickness between 100 nm and 1500 nm.

12. The modulatable infrared emitter according to claim 1, wherein the actuator is a MEMS actuator.

13. The modulatable infrared emitter according to claim 1, wherein the infrared emitter comprises at least four MEMS actuators, which are installed on the outer sides of the cover element and are configured to control the relative movement of the cover element and the base element between the first and second position simultaneously.

14. The modulatable infrared emitter according to claim 1, wherein the cover element is at a distance of at least 500 nm from the dielectric layer in the first position and it is at a distance of at most 200 nm from the dielectric layer in the second position.

15. The modulatable infrared emitter according to claim 1, wherein the cover element and base element have a degree of overlap of less than 40% in the first position, and the cover element and base element have a degree of overlap of more than 40% in the second position.

16. (canceled)

17. (canceled)

18. (canceled)

19. A production method for an infrared emitter according to claim 1, wherein the production comprises the following steps: etching a substrate; depositing a conductive material onto the substrate to form a heatable layer and contacting the heatable layer; depositing a conductive material to form the base element; depositing a dielectric material to form a dielectric interlayer; depositing a conductive material to form a cover element and/or structuring the cover element as a metamaterial with periodically arranged unit cells.

20. (canceled)

21. (canceled)

22. A system, comprising: a modulatable infrared emitter according to claim 1; a control device, wherein the control device is configured for regulating the actuator for a relative movement of the cover element and the base element between a first and second position in order to modulate the intensity of the emission of the infrared emitter.

23. (canceled)

24. The system according to claim 22, wherein the control device is configured to regulate the actuator for an oscillating relative movement of the cover element and the base element between a first and a second position.

25. A method for the modulated emission of infrared radiation, comprising providing a modulatable infrared emitter according to claim 1; heating the heating element to emit infrared radiation; controlling the actuator for a relative movement of the cover element and the base element between a first and second position in order to modulate the intensity of the emission of the infrared emitter.

26. A method of performing photoacoustic spectroscopy and/or infrared spectroscopy comprising using a modulatable infrared emitter according to claim 1.

27. A photoacoustic spectroscope for analyzing gas, comprising a modulatable infrared emitter according to claim 1; an analysis volume that can be filled with gas; and a sound detector, wherein the analysis volume is arranged between the infrared emitter and the sound detector, so that the infrared radiation emitted in a modulatable manner by the infrared emitter can be used for photoacoustic spectroscopy of the gas.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0215] FIG. 1 shows a schematic representation of a cross-section of a preferred embodiment of the modulatable infrared emitter.

[0216] FIG. 2 shows a schematic 3D view of a preferred embodiment of the modulatable infrared emitter.

DETAILED DESCRIPTION OF THE FIGURES

[0217] FIG. 1 shows a schematic representation of a preferred embodiment of a modulatable infrared emitter 1 in cross-section. A layer structure comprising a planar base element 9, a dielectric interlayer 7, and a planar cover element 5 made of a structured metamaterial is present on a heating element 11. The heating element 11 may comprise, for example, an Si substrate onto which a heatable layer made of a conductive material is applied, on which there are contacts for a current and/or voltage source. However, it can also be preferred that the base element 9 functions as a heatable layer and is contacted for this purpose. The base element 9 and the cover element 5 are preferably made from a conductive material, particularly preferably from a metal.

[0218] The cover element 5 is coupled to actuators 3, which are configured for a vertical translational movement of the cover element 5 with respect to the base element and can control at least two positions.

[0219] In a first position (FIG. 1A), the cover element 5 is kept at a greater distance above the dielectric interlayer 7 than in a second position (FIG. 1B).

[0220] For this purpose, in the embodiment shown, there is a spacing frame 13 on the dielectric interlayer 7, which defines the vertical distance between the cover element 5 and the dielectric interlayer 7 in the first position. The spacing frame 13 can be, for example, a nitride or oxide layer, which is applied along the border of the dielectric interlayer 7 at a defined height. The actuators 3 are coupled both to the spacing frame 13 and to the cover element 5 and are configured to hold the cover element 5 at the level of the upper end of the spacing frame 13 in a first position, while the cover element 5 is lowered toward the dielectric interlayer 7, preferably to the point of contacting, in the second position.

[0221] The actuators 3 are preferably MEMS actuators, especially preferably electrostatic MEMS actuators, in which the cover element 5 can be moved into a first or second position in a targeted manner, for example by applying a voltage.

[0222] The translational movement of the cover element 5 controlled by the actuators 3 modulates the intensity of the infrared emitter 1.

[0223] During the operation of the infrared emitter 1, the heating element 11 is preferably controlled to a temperature in a range of from 50° to 1000°. The resulting emitted infrared radiation depends on the distance at which the cover element 5 made of a structured metamaterial is located above the dielectric interlayer 7 or the base element 9.

[0224] In the second position shown in FIG. 1B, the cover element 5 is located at a distance of preferably less than 200 nm, especially preferably at a distance which corresponds to a contact between the two elements. In this state, the cover element 5 made of a structured metamaterial, the dielectric interlayer 7, and the base element 9 on the heating element 11 preferably form a metamaterial perfect absorber, whereby a particularly high emissivity is achieved for one or more preferred resonance wavelengths. In other words, an electromagnetic resonance occurs in the second position, which enables the infrared radiation to be coupled to a specific resonance wavelength.

[0225] The vertical distance in the first position (FIG. 1A) is selected such that no resonant coupling can occur and the infrared emitter 1 has a low emissivity.

[0226] The change provided by the actuators 3 between a first (non-resonant) and a second (resonant) position thus modulates the intensity of the emitted infrared radiation. In simple terms, the IR emitter 1 is “OFF” in the first position and “ON” in the second position. A high-frequency modulation between the two states in the kHz range can advantageously be achieved using MEMS actuators, as a result of which the infrared emitter described is particularly suitable for applications in infrared spectroscopy.

[0227] FIG. 2 shows a schematic 3D view from above of a preferred embodiment of a modulatable infrared emitter 1. This is preferably an embodiment of a modulatable infrared emitter 1 as was explained with reference to the cross-section shown in FIG. 1. As can be seen in the 3D view, the preferred infrared emitter 1 comprises four MEMS actuators 3, which are installed on the outer sides of the cover element 5. The four MEMS actuators 3 are preferably each coupled to the spacing frame 13 and to the cover element 5 and configured for a vertical relative movement of the cover element 5 from a first position (FIG. 2A) to a second position (FIG. 2B). The use of the four MEMS actuators 3 enables the cover element 5 to be lowered particularly quickly and reliably to a desired distance.

[0228] As explained with regard to FIG. 1, the vertical lowering of the cover element 5 made of structured metamaterial onto the dielectric interlayer (not shown) results in a resonant emission of the infrared radiation at one or more preferred resonance wavelengths. In the schematic illustration, the structuring of the metamaterial is indicated by rectangular unit cells. They are primarily used for illustration purposes and, as described above, different shapes and/or dimensions of the unit cells can be used in order to ensure effective resonant emission in the second position.

LIST OF REFERENCE NUMERALS

[0229] 1 Modulatable infrared emitter [0230] 3 Actuator [0231] 5 Cover element made of structured metamaterial [0232] 7 Dielectric interlayer [0233] 9 Base element made of a conductive material [0234] 11 Heating element [0235] 13 Spacing frame

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