Guided-mode-resonant grating-coupled quantum well infrared photodetector for filter-free CH 4 detection

Abstract We propose a guided-mode-resonant (GMR) grating-coupled quantum well infrared photodetector (QWIP) for filter-free CH 4 detection at 7.67 μm. Numerical simulations of an air–dielectric–air GMR structure backed by an Au reflector demonstrate strong synergistic enhancement of guided-mode resonance and a Fabry–Pérot cavity, yielding a peak quantum efficiency (QE) of 75%, an ultra-narrow full width at half maximum (FWHM) of 53 nm (Q ≈ 144.7), and a simulated responsivity of ∼0.64 A W −1 (78 K, 0.5 V). The device maintains peak response at 7.67 μm at angles of incidence up to 40°. By altering the period and etching width, the peak response position can be shifted, whilst adjusting the intrinsic absorption of the quantum well can be employed for detecting other gases. These features allow narrowband gas detection without external filters, reducing system complexity and allowing for applications in hyperspectral imaging.