Doubly resonant sub-ppt photoacoustic gas detection with eight decades dynamic range

Gas sensors with high sensitivity, wide dynamic range, high selectivity, fast response, and small footprint are desirable across a broad range of applications in energy, environment, safety, and public health. However, designing a compact gas sensor with ultra-high sensitivity and ultra-wide dynamic range remains a challenge. Laser-based photoacoustic spectroscopy (PAS) is a promising candidate to fill this gap. Herein, we report a novel method to simultaneously enhance the acoustic and light waves for PAS using integrated optical and acoustic resonators. This increases sensitivity by more than two orders of magnitude and extends the dynamic range by more than three orders of magnitude, compared with the state-of-the-art photoacoustic gas sensors. We demonstrate the concept by exploiting a near-infrared absorption line of acetylene (C2H2) at 1531.59 nm, achieving a detection limit of 0.5 parts-per-trillion (ppt), a noise equivalent absorption (NEA) of 5.7×10-13 cm-1 and a linear dynamic range of eight orders of magnitude. This study enables the realization of compact ultra-sensitive and ultra-wide-dynamic-range gas sensors in a number of different fields.