ACS Photon. http://doi.org/b6w2 (2017)

Credit: ACS

An on-chip narrowband thermal light emitter operating in the mid-infrared wavelength range has been developed by scientists in Switzerland. The device, which could help simplify gas sensing, combines microelectromechanical system (MEMS) heater technology with metamaterial emitter structures. From bottom to top, the emitter consists of a complementary metal-oxide–semiconductor (CMOS) substrate, a MEMS hotplate, a metamaterial perfect emitter (MPE) structure with cross-shaped top resonators, and an Al2O3 sealing layer. The metamaterial unit cell dimensions (rectangular array with a periodicity of 2.243 μm, top resonator length of 963 nm, and top resonator width of 187 nm) were designed for maximum emissivity at a resonance wavelength of 4.04 μm with a full-width at half-maximum of 254 nm, which corresponded to a quality factor of 15.9. The MPE area was 4 mm × 4mm, containing 3.2 × 106 unit cells. The emitter and a thermopile detector were both located in a measurement container filled with CO2. The sensitivity of the MPE sensor system was 1.7 × 10−4% per ppm, which is a 5-fold increase in relative sensitivity compared with a conventional blackbody emitter.