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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.94\times 10^{-10}$ </tex-math></inline-formula> cm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}\cdot $ </tex-math></inline-formula>W<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>Hz<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1/2}$ </tex-math></inline-formula>. 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.