基于空心光波导的激光吸收光谱氨气传感器

空心光波导(hollow waveguide, HWG)可以同时传输红外激光和目标气体，是激光气体传感器中的新型气体池，具有体积小、响应速度快的特点。基于可调谐二极管激光吸收光谱(TDLAS)技术，以空心光波导为气体池，研制了氨气激光传感器。采用波长调制光谱(wavelength modulation spectroscopy, WMS)技术，同时解调气体吸收的一次谐波(1f)和二次谐波(2f)信号，通过1f归一化2f信号实现免校准(calibration-free)测量。利用标准气体进行验证实验，结果表明，传感器的响应线性度R2为0.999 8，响应时间24 s。Allan方差结果表明积分时间18 s时检测限为26 ppbv。该传感器可以用于空气中痕量氨气的快速、高灵敏检测。

The Development of Ammonia Sensor Based on Tunable Diode Laser Absorption Spectroscopy with Hollow Waveguide

Hollow waveguides(HWG)have recently emerged as a novel concept serving as an efficient optical waveguide and a highly miniaturized gas cell.Compared with conventional multi-pass gas cells,HWG gas cell has the advantages of facilitating gas exchanging because of its small size and fast responding speed.In this paper,we poposed an ammonia sensor based on tuna-ble diode laser absorption spectroscopy(TDLAS)using HWG as the gas cell.The sensor employs wavelength modulation spec-trum(WMS)with simultaneous detection of the second harmonic(2f)signal and the first hamonic(1f)signal.Normalization of the 2f signal by the 1f signal enables the sensor for calibration free measurement.The sensor performance is tested with gas standards and the result shows good linearity with correlation coefficient of 0.999 8,and the detection limit is 26 ppb with an integration time of 18 s.The sensor based on HWG gas cell is suitable for sensative and real-time monitoring ammonia in the air.