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针对传统腔衰荡光谱技术浓度获取率低,提出基于双重锁定的连续波腔衰荡吸收光谱技术.通过波长调制一次谐波信号将激光器的频率锁定到C_2H_2吸收线上,同时使用PDH锁频技术将衰荡腔锁定到激光器上,从而避免了测量过程中激光器的频率漂移和腔长的抖动,使测量结果更加精确;并且,由于双重锁定,单次衰荡事件的发生率,也就是浓度信息的获取率只受衰荡时间以及重新锁定时间限制,在本试验系统中采集速率可以达到30 k Hz,可以实现对气体浓度的快速测量.为了提高信噪比,采用Kalman滤波技术,对浓度信息进行实时处理,有效抑制了噪声,根据阿伦方差分析,探测灵敏度可以达到4×10~(-9)cm~(-1)(2 s平均).
Aiming at the low acquisition rate of traditional ring-down spectroscopy technique, a double-locked continuous-wave cavity ring-down spectroscopy (EBSA) absorption spectroscopy technique is proposed. The first harmonic signal is wavelength-locked to the C_2H_2 absorption line, Lock the ring to the laser, thus avoiding the laser frequency drift and cavity length jitter during measurement, making the measurement more accurate; and, due to double locking, the incidence of a single ring-down event, known as concentration information The acquisition rate is limited only by the time of asynchronism and the time of re-locking, the acquisition rate can reach 30 k Hz in this experimental system, which can measure the gas concentration rapidly.In order to improve the signal-to-noise ratio, Kalman filter technique is used to measure the concentration information Real-time processing can effectively suppress the noise. According to Allen analysis of variance, the detection sensitivity can reach 4 × 10 -9 cm -1 (2 s average).