光声光谱法是检测气体最灵敏的方法,气体浓度检测精度可达到ppt量级,但这需要复杂的实验系统和昂贵的器材,不利于在工程实践上使用.本文基于可调激光器的电流调制特性,提出了一种在测量气体吸收谱的吸收零点和吸收峰之间有效切换波长的简单调制方法.当激光功率为2.1 mW时,甲烷气体浓度的测量极限可达到0.46 ppm,测量结果证明了双波长法的可行性.

Photoacoustic spectroscopy is the most sensitive approach of trace gas analysis reaching part per trillion by volume level and available for engineering practice, but not sufficiently satisfy the measurement demand of gases with weak absorption in near infrared zone. This paper presents a simple interrogation method using a dual-wavelength schema to switch effectively between the absorption and unabsorption lines of the gas to be measured, which takes good advantage of the current modulation characteristic of laser diode. Measurement results of methane demonstrate the feasibility and a relatively simple way to reach resolution of 0.46 ppm of the dual-wavelength method when the laser power is 2.1 mW.