On-Chip Narrowband Thermal Emitter for Mid-IR Optical Gas Sensing

Efficient light sources compatible to complementary metal oxide semiconductor (CMOS) technology are key components for low-cost, compact mid-infrared gas sensing systems. In this work we present an on-chip narrowband thermal light source for the mid-infrared wavelength range by combining microelectromechanical system (MEMS) heaters with metamaterial perfect emitter structures. Exhibiting a resonance quality factor of 15.7 at the center wavelength of 3.96 μm and an emissivity of 0.99, the demonstrated emitter is a spectrally narrow and efficient light source. We show temperature-stable (resonance wavelength shift 0.04 nm/°C) and angular-independent emission characteristics up to angles of 50° and provide an equivalent circuit model illustrating the structure’s resonance behavior. Owing to its spectrally tailored, nondispersive emission, additional filter elements in a free-space optical gas sensing setup become obsolete. In a proof-of-concept demonstration of such a filter-free gas sensing system with CO₂ concentrations in the range of 0–50000 ppm, we observe a 5-fold increase in relative sensitivity compared to the use of a conventional blackbody emitter. Our light source is fully compatible with standard CMOS processes and tunable in emission wavelength through the mid-infrared wavelength band. It paves the way for a new class of highly integrated, low-cost optical gas sensors

Data File 1: Harnessing nonlinearities near material absorption resonances for reducing losses in plasmonic modulators

Refractive Index of 75%HD-BB-OH and 25%YLD124 Originally published in Optical Materials Express on 01 July 2017 (ome-7-7-2168