Photonic- and phononic-structured pixel for electromagnetic radiation and detection
View Patent ↗A thermal pixel configured as an electromagnetic emitter and/or an electromagnetic detector. The thermal pixel comprises a micro-platform suspended with semiconductor nanowires from a surrounding support platform. The nanowires comprise phononic structure providing a decrease in thermal conductivity. In some embodiments, the pixel is structured for operation within a broad bandwidth or a limited bandwidth. Metamaterial and/or photonic crystal filters provide pixel operation over a limited bandwidth. In some other embodiments, the micro-platform comprises a nanotube structure providing a broadband emission/absorption spectral response.
1. An electromagnetic thermal pixel (ETP) including photonic structure and phononic structure, the ETP comprising:
a substrate having a substantially planar surface;
a cavity formed from the substrate;
a thermal micro-platform disposed within the cavity and suspended from the substrate by a plurality of nanowires; wherein,
the phononic structure comprises:
(i) a first layer of semiconductor disposed within at least one of the nanowires of the plurality, the first layer providing electrical conductivity;
(ii) a phononic scattering structure and/or phononic resonant structure providing a reduction in thermal conductivity;
the photonic structure comprises:
(i) photonic nonresonant structure and/or photonic resonant structure providing emissivity and/or absorptivity of electromagnetic radiation within a range of one or more of visible, NIR, MWIR, LWIR, and millimeter wavelengths, and
wherein the ETP further comprises at least one of a temperature sensor, a resistive heater, an infrared radiation source, a Peltier cooler, and a self-cooling micro-refrigerator.
2. The ETP of claim 1 wherein the ETP is disposed in an array of ETPs.
3. The ETP of claim 1 wherein the phononic scattering structure comprises scattering sites separated by distances less than a mean-free-path of heat-conducting phonons.
4. The ETP of claim 3 comprising porous silicon.
5. The ETP of claim 1 wherein the phononic resonant structure comprises a phononic crystal (PnC) having a phononic bandgap.
6. The ETP of claim 1 wherein the phononic structure comprises holes, vias, surface pillars, surface dots, plugs, cavities, implanted atomic species, local particulates, and molecular aggregates.
7. The ETP of claim 1 wherein the first layer of semiconductor is selected from the group consisting of Si, Ge, SiGe, GaAs, GaN, InP, SiC, TiN, Bi 2 Te 3 , Bi 2 Se 3 , CoSb 3 , Sb 2 Te 3 , La 3 Te 4 , SnSe, ZnS, CdS, and semiconducting alloys/superlattice combinations thereof.
8. The ETP of claim 1 wherein the phononic structure further comprises an ALD metal layer or metallic interstitial layer selected from the group consisting of aluminum, tungsten, palladium, platinum, molybdenum.
9. The ETP of claim 1 wherein the phononic structure further comprises a dielectric layer comprising at least one material selected from the group consisting of silicon dioxide, silicon nitride, hafnium oxide, silicon oxynitride, and aluminum oxide, wherein the dielectric layer provides insulation between electrically conducting layers and/or a control of mechanical stress.
10. The ETP of claim 1 wherein the photonic resonant structure comprises at least one of a LC resonator, a split ring resonators (SRR), a photonic crystal (PhC) having deep-subwavelength dimensions providing an increase in emissivity and/or absorptivity within a limited wavelength range.
11. The ETP of claim 1 comprising at least one of a wavelength antenna and fractile antenna.
12. The ETP of claim 1 wherein the photonic nonresonant structure comprises at least one of carbon nanotubes, graphene mesh, gold black, carbon black and silicon grass, wherein the photonic nonresonant structure provides an increase in emissivity and/or absorptivity within a broadband wavelength range.
13. The ETP of claim 1 comprising the resistive heater, wherein the resistive heater comprises a gettering material, and when the resistive heater is enabled, the resistive heater increases a level of vacuum within the cavity.
14. The ETP claim 1 comprising the temperature sensor, wherein the temperature sensor comprises at least one of a Seebeck thermoelectric sensor, thermistor, subthreshold MOS, and bolometer.
15. The ETP of claim 1 wherein the photonic structure comprises a reverse-biased pn junction diode.
16. The ETP of claim 1 wherein the Peltier cooler cools the micro-platform.
17. The ETP of claim 1 comprising the self-cooling micro-refrigerator, wherein the self-cooling micro-refrigerator is disposed in the cavity and is hermetically sealed and maintained in a vacuum condition, and further wherein the one or more of the nanowires provide thermal isolation from the substrate sufficient for the micro-platform to cool spontaneously via emitted thermal radiation.
18. The ETP of claim 1 comprising the resistive heater, wherein the resistive heater is operated to provide a photonic source of electromagnetic radiation.
19. The ETP of claim 1 wherein the resistive heater or the temperature sensor provide a photonic source or photonic detector, respectively, within a photospectrometer or pyrometer.
20. The ETP of claim 1 comprising the resistive heater or temperature sensor providing a photonic source or photonic detector, respectively, within a photonic communication system.