Development of ultra high resolution mid-infrared molecular spectrometer combining advanced sources

在86.8-93.1太赫兹范围内进行了甲烷的亚多普勒分辨光谱测量，测得204个跃迁频率，其不确定度为几千赫兹。结果列在HITRAN 2014数据库中。差频产生的泵浦频率和信号频率稳定在光频梳上，并通过改变重复频率来扫描空闲频率，以记录甲烷、甲基碘和氯化氢的弱谱线。利用加强型腔吸收池与宽光束耦合，将饱和谱线的宽度减小到80 kHz，双梳光谱的光频梳相对谱线宽度减小到1 Hz以下，记录了1.0~1.8微米的吸收光谱，光谱分辨率为48 MHz，采集时间为140ms。

Sub-Doppler resolution spectroscopy of methane has been carried out from 86.8 to 93.1 THz, and 204 transition frequencies have been determined with an uncertainty of a few kHz. The results are listed in HITRAN 2014 database. The pump and signal frequencies for difference-frequency-generation are stabilized to the optical frequency comb, and the idler frequency is swept by varying the repetition rate to record weak spectral lines of methane, methyl iodine, and hydrogen chloride. An enhanced-cavity absorption-cell coupled with a wide beam reduces the width of the saturation lines to 80 kHz.The relative spectral linewidth of the optical frequency combs for dual-comb spectroscopy is reduced below 1Hz, and absorption spectrum from 1.0 to 1.8 micron m is recorded with a spectral resolution of 48 MHz and an acquisition time of 140 ms.