UV-Nanoimprinted Metasurface Thermal Emitters for Infrared CO2 Sensing

A polarization- and angle-independent dual-band metasurface thermal emitter for CO2 sensing was developed. The metasurface was based on a stacked Au/Al2O3/Au structure in which orthogonal rectangular Au patches were alternately arrayed, generating nearly perfect blackbody radiation with emittance as high as 0.98 at 4.26 and 3.95 μm. The metasurface was integrated on a Joule heater fabricated on a SiN membrane so that infrared light is radiated by applying voltage. Subwavelength-sized metasurfaces were manufactured by mass-producible, cost-effective ultraviolet nanoimprint lithography, and the emitter chip was mounted on a standard package compatible with conventional optoelectronic devices. A simple single-layer lift-off process was enabled by employing an organic-solvent-soluble UV resist. The metasurface emitter was applied to a CO2 sensor and was demonstrated to reduce required electric power by 31% as compared with a conventional blackbody emitter, due to the suppressed unnecessary radiation. Results demonstrate that commercialization of metasurface infrared thermal emitters is becoming a reality.