Miniature FT-MIR using a MEMS interferometer with a metasurface emitter and detector
A miniature Fourier transform mid-infrared (FT-MIR) spectrometer is provided. The FT-MIR includes a metasurface IR source to emit radiation when heated, a microelectromechanical (MEMS) interferometer, and a metasurface microbolometer to measure an interferogram from the MEMS interferometer, wherein the miniature FT-MIR spectrometer is less than about 20 mm in outer diameter.
1. A mid-infrared (MIR) spectrometer, comprising:
a metasurface IR source to emit radiation when heated, wherein the metasurface IR source comprises an electrically conductive geometric pattern based on a geometric inversion of the Rhodonea conformal mapping contours; and
a metasurface microbolometer to detect the radiation from the metasurface IR source.
2. The MIR spectrometer of claim 1 , wherein the metasurface IR source comprises an electrically conductive geometric pattern based on a geometric inversion of the Tangent Circles conformal mapping contours.
3. The MIR spectrometer of claim 1 , wherein the metasurface IR source is tuned to emit radiation from about 500 wavenumbers (cm −1 ) to about 2000 cm −1 .
4. The MIR spectrometer of claim 1 , wherein the metasurface IR source comprises a heating filament to heat the metasurface IR source to about 900 K.
5. The MIR spectrometer of claim 1 , wherein the metasurface microbolometer comprises:
a metasurface tuned to adsorb radiation in a range of frequencies in the mid infrared;
a thermometric layer in contact with the metasurface, wherein the thermometric layer changes in resistivity with temperature changes;
a dielectric substrate supporting the thermometric layer and the metasurface; and
a readout integrated circuit to measure a response from the thermometric layer comprising a voltage drop across the contacts of the bridge with a constant bias current.
6. The MIR spectrometer of claim 5 , wherein the metasurface is tuned to adsorb radiation from about 500 wavenumbers (cm −1 ) to about 2000 cm −1 .
7. The MIR spectrometer of claim 5 , wherein the metasurface comprises gold.
8. The MIR spectrometer of claim 5 , wherein the metasurface absorbs light through surface plasmon resonances.
9. The MIR spectrometer of claim 5 , wherein the metasurface is about 120 nm in thickness.
10. The MIR spectrometer of claim 5 , wherein the metasurface is less than 30 nm in thickness.
11. The MIR spectrometer of claim 5 , wherein the metasurface has a diameter of about 150 μm.
12. The MIR spectrometer of claim 5 , wherein the metasurface has a 35% fill factor.
13. The MIR spectrometer of claim 5 , wherein the metasurface has a detectivity (D*) of about 1×10 10 cm*sqrt(Hz)/W at 333 K at a bias current of 75 μA.
14. The MIR spectrometer of claim 5 , wherein the metasurface has a noise equivalent difference temperature (NEDT) of about 1 mK at a bias current of 75 μA.
15. The MIR spectrometer of claim 5 , wherein the thermometric layer comprises undoped vanadium oxide (VO 2 ).
16. The MIR spectrometer of claim 5 , wherein the thermometric layer is about 500 nm in thickness.
17. The MIR spectrometer of claim 5 , wherein the dielectric substrate comprises silicon nitride (Si 3 N 4 ).
18. The MIR spectrometer of claim 5 , wherein the dielectric substrate is about 200 nm in thickness.
19. The MIR spectrometer of claim 5 , wherein the dielectric substrate is about 100 nm in thickness.
20. The MIR spectrometer of claim 5 , wherein the dielectric substrate is separated from the readout integrated circuit by an airgap.
21. The MIR spectrometer of claim 5 , wherein the metasurface microbolometer has a broadband absorption of more than 90% in a wavenumber range of about 1500 to about 600 cm −1 .
22. The MIR spectrometer of claim 1 , wherein the metasurface microbolometer has an absorption bandwidth of 156% of full width half maximum (FWHM) centered on a wavenumber of 1070 cm −1 .