一种高Q值椭圆差分共振光声腔的理论研究

Theoretical Research on a High Q Factor Elliptical Differential Photoacoustic Resonator

光声腔的性能是决定光声光谱检测灵敏度的重要因素。为了增强光声光谱检测系统的信噪比和抗干扰能力,本文首次提出一种新型的椭圆差分共振光声腔,建立了其声学特征模型并利用COMSOL软件对光声腔的声学特性进行仿真研究。研究结果表明,当椭圆截面上的混合模态在短轴方向存在奇数个角向波节时,长轴两端声压达到峰值且相位反相;当椭圆腔的半长轴长度低于4cm时,谐振频率能达到10kHz以上,Q值可达到1 835。基于这种椭圆差分光声腔,可实现光声信号的差分检测,抑制环境共模噪声;利用共振腔的高Q值特性,能有效地增强系统信噪比,实现高灵敏度的光声检测。

The sensitivity of photoacoustic （PA） sensors strongly depends on the characteristic of PA cell. In the present paper, a novel elliptical differential PA cell was proposed to enhance the signal noise ratio of PA system. An acoustic characteristic mathematic model was built and the acoustic characteristic of PA cell was simulated with COMSOL software. The result shows that peak pressures would occur at the two ends of major axis with a n phase difference when the mixed modes in the cross sec- tion of elliptical cell have odd azimuthal nodes along the minor axis. When the half major axis is less than 4 cm, the resonant fre- quency could be greater than 10kHz and the Q factor could achieve 1 835. Differential detection of PA signal could be realized and the common mode environment noise would be suppressed effectively. The signal noise ratio can he enhanced and high sensitivity detection could be achieved with this high Q factor elliptical differential cell.