Wide-range adaptive piezoelectric MEMS-Fabry-Pérot filter for gas spectral identification

Infrared spectroscopy ranks among the most extensively employed analytical techniques for gas spectral identification applications. Conventional infrared spectrometers, however, are often plagued by inherent limitations, including a large physical footprint, high costs, and an inevitable trade-off between spectral resolution and optical throughput. To address these issues, this study proposes a piezoelectric micro-electro-mechanical systems (MEMS) tunable Fabry-Perot filter (FPF) fabricated using a 4-inch wafer-level bonding process. The FPF features a large optical aperture of 3.2 mm and a sweeping rate of 250 Hz. The FPF cavity length is tunable by four pairs of piezoelectric-driven folded beams. Parallelism can be further optimized through applying a DC voltage to each beam individually, thereby achieving a low dynamic deformation and, thus an approximate 10% improvement in transmittance is obtained. This design achieves a free spectral range (FSR) of 101.6 nm, full width at half maximum (FWHM) below 3 nm, and an optimized peak transmission exceeding 90%. Ultimately, through the constructed gas spectral identification system, the MEMS-FPF-based near-infrared spectrometer achieved transmission spectral identification of C₂H₂ and HCN gases in the tuning frequency range of 100 Hz.