Double Resonant Cavity Enhanced Photoacoustic Gas Sensor for Acetylene Detection

In order to achieve highly sensitive gas detection, we proposed and experimentally demonstrated a doubly resonant cavity enhanced photoacoustic (CEPA) gas sensing technology. Two high-reflection mirrors were added on both sides of the H-type photoacoustic (PA) cell to form a CEPA cell. As an example, we developed an acetylene (C2H2) gas sensor. Double resonance of optical and acoustic greatly improves the detection sensitivity, achieving a 60-time enhancement of PA signal. Compared with other sensors of the same type, the proposed sensor exhibits excellent performance with a limit of detection (LoD) of six parts-per-billion (ppb) and a normalized noise equivalent absorption (NNEA) coefficient of $1.94\times 10^{-10}$ cm $^{-1}\cdot $ W $\cdot $ Hz $^{-1/2}$ . By increasing the reflectivity of mirrors and optimizing the mode matching conditions of the laser cavity, the LoD of proposed sensor can be further improved.