Thin film emitter-absorber apparatus and methods
Methods and apparatus for providing a tunable absorption-emission band in a wavelength selective device are disclosed. A device for selectively absorbing incident electromagnetic radiation includes an electrically conductive surface layer including an arrangement of multiple surface elements. The surface layer is disposed at a nonzero height above a continuous electrically conductive layer. An electrically isolating intermediate layer defines a first surface that is in communication with the electrically conductive surface layer. The continuous electrically conductive backing layer is provided in communication with a second surface of the electrically isolating intermediate layer. When combined with an infrared source, the wavelength selective device emits infrared radiation in at least one narrow band determined by a resonance of the device. In some embodiments, the device includes a control feature that allows the resonance to be selectively modified. The device has broad applications including gas detection devices and infrared imaging.
1. A tunable device for selectively coupling electromagnetic radiation comprising:
a first electrically conductive layer including a plurality of discrete surface elements formed on or in the layer;
an electrically insulating intermediate layer defining a first surface in communication with the electrically conductive surface layer;
a second, continuous electrically conductive layer in communication with a second surface of the electrically insulating intermediate layer; and
an electrode in electrical communication with at least one of the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous, electrically conductive layer, the plurality of discrete surface elements resonantly coupling at least a portion of the electromagnetic radiation with respect to the continuous electrically conductive layer;
wherein the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous, electrically conductive layer form a wavelength selective element having at least one reflection or absorption-emission band; and
wherein the wavelength selective element comprises a material having a material property that is variable in response to an external signal applied to the device, and wherein variation of the material property tunes the at least one reflection or absorption-emission band.
2. The device of claim 1 , wherein the plurality of discrete surface elements comprises an array of uniform-sized electrically conductive elements.
3. The device of claim 2 , wherein the uniformly shaped elements are selected from the group consisting of: closed curves; ellipses; circles; rectangles; squares; polygons; triangles; hexagons; parallelograms; stars having at least three legs; annular structures; and combinations thereof.
4. The device of claim 1 , wherein the plurality of discrete surface elements are arranged in an array.
5. The device of claim 4 , wherein the array is selected from the group consisting of: rectangular grids; square grids; triangular grids; Archimedean grids; and random arrangements.
6. The device of claim 1 , wherein at least one of the first and second electrically conductive layers is formed from a metal.
7. The device of claim 1 , wherein the electrically insulating intermediate layer comprises a dielectric material.
8. The device of claim 1 , wherein at least one of the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous electrically conductive layer comprises a semiconductor.
9. The device of claim 1 , wherein the plurality of discrete surface elements of the first electrically conductive layer comprises a plurality of through holes defined in an electrically conductive surface layer.
10. The device of claim 9 , wherein the plurality of discrete through holes comprises an array of uniform-sized elements.
11. The device of claim 1 , wherein the second, continuous electrically conductive layer comprises an electrically activated thermal source in communication with the electrode, the electrode receiving an electrical input to activate the thermal source.
12. The device of claim 1 , wherein the second, continuous electrically conductive layer comprises a thermistor in thermal communication with the plurality of discrete surface elements and in communication with the electrode, the electrode enabling remote monitoring of the thermistor.
13. The device of claim 1 , wherein two or more of the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous, electrically conductive layer are configured to provide a controllable switch, the electrode receiving an electrical input for controlling the switch.
14. The device of claim 1 , wherein the external signal comprises at least one selected from the list consisting of: an electrical signal, a chemical signal, an optical signal, and a thermal signal.
15. The device of claim 1 , wherein the material property comprises conductivity.
16. A tunable infrared emitter comprising:
a first electrically conductive layer including a plurality of discrete surface elements formed on or in the layer;
an electrically insulating intermediate layer defining a first surface in communication with the electrically conductive surface layer;
a second, continuous electrically conductive layer in communication with a second surface of the electrically insulating intermediate layer; and
an infrared source in thermal communication with at least one of the first electrically conductive layer, the electrically insulating layer and the second, continuous electrically conductive layer, the infrared source generating broadband infrared radiation, the plurality of discrete surface elements electromagnetically coupling at least a portion of the broadband infrared radiation,
wherein the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous, electrically conductive layer form a wavelength selective element having at least one infrared reflection or absorption-emission band; and
wherein the wavelength selective element comprises a material having a material property that is variable in response to an external signal applied to the device, and wherein variation of the material property tunes the at least one reflection or absorption-emission band; and
wherein the wavelength selective element interacts with the broadband infrared radiation to produce a narrowband infrared emission.
17. The device of claim 16 , wherein tuned, narrowband infrared emission has a selectivity of not more than about 0.1, determined at a full-width-half-maximum spectral width.
18. The device of claim 16 , wherein the infrared source comprises an electrical filament.
19. The device of claim 18 , wherein the electrical filament includes the second, continuous electrically conductive layer.
20. The device of claim 16 , wherein a total thickness of the first electrically conductive layer, the electrically insulating layer and the second, continuous electrically conductive layer is not more than about 10 μm.
21. The device of claim 20 , wherein the device is suspended above a surface.
22. The device of claim 16 , further comprising a thermistor in thermal communication with the plurality of discrete surface elements, the device selectively emitting infrared radiation in a tuned band determined by the electromagnetic coupling of the plurality of discrete surface elements.
23. The device of claim 16 , wherein the external signal comprises at least one selected from the list consisting of: an electrical signal, a chemical signal, an optical signal, and a thermal signal.
24. The device of claim 16 , wherein the material property comprises conductivity.
25. A controllable wavelength selective device, comprising:
a first electrically conductive layer including a plurality of discrete surface elements formed on or in the layer;
an electrically insulating intermediate layer defining a first surface in communication with the electrically conductive surface layer;
a second, continuous electrically conductive layer in communication with a second surface of the electrically insulating intermediate layer, wherein at least one of the first electrically conductive layer; the electrically insulating intermediate layer; and the second, continuous electrically conductive layer comprises a material having an electrical conductivity which is controlled in response to an external signal applied to the device;
wherein the first electrically conductive layer, the electrically insulating intermediate layer, and the second continuous, electrically conductive layer form a wavelength selective element having at least one reflection or absorption-emission band; and
wherein a property of the at least one reflection or absorption-emission band is controlled in response to the conductivity of the material.
26. The device of claim 25 , wherein at least one of the first electrically conductive layer and the second, continuous electrically conductive layer comprises an electrical conductivity controllable between conducting and non-conducting, the controlled conductivity usable to control resonant performance of the device.
27. The device of claim 26 , wherein at least one of the first electrically conductive layer and the second, continuous electrically conductive layer comprises a semiconductor material having a controllable electrical conductivity responsive to an electrical input.
28. The device of claim 26 , wherein at least one of the first electrically conductive layer and the second, continuous electrically conductive layer comprises a pyroelectric material having a controllable electrical conductivity responsive to a thermal input.
29. The device of claim 25 , wherein the electrically insulating intermediate layer comprises an electrical conductivity controllable between insulating and non-insulating, the controlled conductivity usable to control resonant performance of the device.
30. The device of claim 29 , wherein the electrically insulating intermediate layer comprises a semiconductor material having a controllable electrical conductivity responsive to an electrical input.
31. The device of claim 29 , wherein the electrically insulating intermediate layer comprises a pyroelectric material having a controllable electrical conductivity responsive to a thermal input.
32. The device of claim 29 , wherein the electrically insulating intermediate layer comprises an optically responsive material having a controllable electrical conductivity responsive to an optical input.
33. The device of claim 29 , wherein the electrically insulating intermediate layer comprises a chemically responsive material having a controllable electrical conductivity responsive to a change in a local chemical environment.
34. The device of claim 25 , wherein the external signal comprises at least one selected from the list consisting of: an electrical signal, a chemical signal, an optical signal, and a thermal signal.
35. A method of manufacturing a wavelength selective device comprising:
forming a continuous, electrically thin conductive ground layer on a substrate;
applying an electrically thin insulating layer to a top surface of the ground layer;
forming an electrically thin outer conductive layer on the electrically thin insulating layer,
forming a plurality of discrete surface elements on or in the outer conductive layer;
forming a wavelength selective element having at least one infrared reflection or absorption-emission band comprising the electrically thin conductive ground layer, the electrically thin insulating layer, and the electrically thin outer conductive layer; and
wherein forming the wavelength selective surface comprises forming the wavelength selective surface to comprise a material having a material property that is variable in response to an external signal applied to the device, wherein variation of the material property tunes the at least one reflection or absorption-emission band.
36. The method of claim 35 , wherein at least one of the layers is deposited using a thin film deposition technique.
37. The method of claim 35 , wherein the discrete surface elements are formed using at least one of: laser ablation, removing selected regions of the conductive material from the surface; nano-imprinting; stamping; and standard semiconductor fabrication techniques.
38. The method of claim 35 , wherein the substrate is flexible.
39. The method of claim 35 , further comprising removing a sacrificial layer between a bottom surface of the ground layer and a substrate, removal of the sacrificial layer releasing a multi-layered thin-film device.
40. The method of claim 39 , wherein the thickness of the multi-layered thin-film device is not more than about 10 μm.
41. The method of claim 35 , wherein the external signal comprises at least one selected from the list consisting of: an electrical signal, a chemical signal, an optical signal, and a thermal signal.
42. The method of claim 35 , wherein the material property comprises conductivity.