一次谐波锁频的快速光腔衰荡光谱检测

本文介绍了一种赫兹级响应速率的光腔衰荡光谱探测大气痕量气体的检测技术.将100 MHz正弦波调制信号加载在电光相位调制器上产生边带,用混频器提取载波与边带通过3m气体吸收池后拍频所产生的一次谐波作为误差信号,实现了1572 nm分布式反馈激光器对于二氧化碳气体分子6361.25 cm-1处超精细跃迁线的频率锁定.采用波...

Fast optical cavity ring-down spectroscopy detection based on first harmonic frequency locking

Optical cavity ring-down spectroscopy with a Hz-level response rate is introduced to detect trace gases in the atmosphere.By loading a 100 MHz modulated sine wave signal on the electro-optic phase modulator that generates sidebands and using the mixer to extract the first harmonic generated as the error signal by the beat frequency of the carrier and sidebands after passing through the 3 m gas absorption cell,the frequency locking of a 1572 nm distributed feedback laser on the 6361.25 cm^-1 hyperfine transition line of carbon dioxide gas molecule was achieved.The ring-down time of the cavity without gas and the ring-down time with gas absorption were simultaneously measured using the wavelength-division multi?plexing method,and the detection limit of the system obtained was 4.82×10^-10 cm^-1 on a 330 mm optical resonator.The system has a good linear response in a large carbon dioxide concentration range,and the linear correlation coefficient is greater than 0.999.The long-term observation results of the system are highly consistent with the data from Picarro commercial instruments,and the deviation between the two is less than 1.0%.The system proved the feasibility of locking the laser frequency to the molecular hyperfine transition line using the first harmonic and applying it to the optical cavity ring-down spectroscopy system to achieve a fast trace gas detection.