Conductor-backed dielectric metasurface thermal emitters for mid-infrared spectroscopy

A conductor-backed dielectric metasurface thermal emitter at mid-IR frequencies with narrowband emissivity is experimentally demonstrated. The metasurface emitter consists of a high permittivity silicon resonator on top of a ground plane, whose resonant mechanism is explained using image theory. The resonator, placed close to a copper ground plane, is designed to produce a magnetic resonance, resulting in a low-profile device with a single emission peak in its subwavelength frequency range. The thermal emitter is next fabricated using common CMOS processes. Frequency dependent optical constants of plasma-enhanced chemical vapor deposited films of Si, SiO2, and evaporated Cu are also reported in the mid-IR range. Narrowband thermal emission is successfully obtained at around 7.22μm (41.5 THz), which corresponds to the absorption band of SO2. The Q-factor of about 37 is achieved with a peak emissivity of 0.65, which is significantly higher compared to the reported Q-factors of state-of-the-art plasmonic resonators.