Room-temperature mid-infrared detection using metasurface-absorber-integrated phononic crystal oscillator

Abstract

Mid-infrared (MIR) detectors find extensive applications in chemical sensing, spectroscopy, communications, biomedical diagnosis and space explorations. Alternative to semiconductor MIR photodiodes and bolometers, mechanical-resonator-based MIR detectors show advantages in higher sensitivity and lower noise at room temperature, especially towards longer wavelength infrared. Here, we demonstrate uncooled room-temperature MIR detectors based on lithium niobate surface acoustic wave phononic crystal (PnC) resonators integrated with wavelength-and-polarization-selective metasurface absorber arrays. The detection is based on the resonant frequency shift induced by the local temperature change due to MIR absorptions. The PnC resonator is configured in an oscillating mode, enabling active readout and low frequency noise. Compared with detectors based on tethered thin-film mechanical resonators, our non-suspended, fully supported PnC resonators offer lower noise, faster thermal response, and robustness in both fabrication and practical applications. Our 1-GHz oscillator-based MIR detector shows a relative frequency deviation of $5.24 \times 10^{-10}$ Hz$^{-1/2}$ at an integration time of 50 ${\mu}$s, leading to an incident noise equivalent power of 197 pW/$\sqrt{\mathrm{Hz}}$ when input 6-${\mu}$m MIR light is modulated at 1.8 kHz, and a large dynamic range of 107 in incident MIR power. Our device architecture is compatible with the scalable manufacturing process and can be readily extended to a broader spectral range by tailoring the absorbing wavelengths of metasurface absorbers.