Long-wave and mid-wave infrared micro-bolometers with gold black or wavelength-selective absorbers

This paper highlights our recent work on wavelength-selective air-bridge infrared bolometers for the 8-12 and 3-5 micron wavelength bands. Gold-black coatings specially protected to enable patterned deposition on bolometer arrays have provided enhanced dual band sensitivity. Subwavelength metal-insulator-metal (MIM) resonant structures were patterned on individual air-bridge bolometers to provide design-tunable enhancement of absorption, which can be engineered to span the 8-12 micron band, or to select narrowly within each considered band for infrared spectral sensing. The choice of MIM dielectric depends critically on refractive-index dispersion at the wavelengths of interest. Integrating the bolometric material within the MIM absorber, and minimizing layer thicknesses, can optimize detector speeds. Deposition of nanocrystalline VOx and TiO2 by aqueous-spray heterogeneous chemical reaction is investigated as a means of producing bolometric thin films and MIM dielectrics, respectively.