光频链接的双光梳气体吸收光谱测量

Optical frequency linked dual-comb absorption spectrum measurement

双光梳光谱技术以其无运动部件快速采样、高分辨率探测等优势成为宽带激光光谱测量中的热点技术.但受限于常用微波锁定双光梳光源间的噪声特性,双光梳光谱技术仍难以发挥其探测潜能.本文报道一种光频域互相链接的双光梳光谱探测方案.通过将两台激光器的偏置频率同时锁定到一个窄线宽激光器上,既免去了结构复杂且成本高昂的非线性自参考系统,又将双光梳间的共同参考点设置到了光频范围,抑制了双光梳光谱采样抖动,实现光谱探测性能的提升.^(13)C_2H_2的ν_1+ν_3 P支光谱数据测量数据分析结果表明:谱线位置与文献结果符合良好,光谱分辨率为0.086 cm^(-1),信噪比>200:1(62.5 ms,100幅平均),相应的秒均噪声等效吸收系数达6.0×10^(-6)cm^(-1)·Hz^(-1/2).该工作为双光梳光谱测量的实际应用提供了一种高精度、低成本、易于实现的解决方案.

Dual-comb spectroscopy is becoming a highlighted topic in broadband spectrum measurement techniques because of two outstanding advantages. One is its highly stable output frequency, which leads to an appealing resolution, and the other is the omitting of moving parts, which helps achieve extreme fast sampling rate. Utilizing the traditional radio frequency linked combs, however, obstructs the dual-comb spectroscopy reaching satisfied performance because the phase noise of the radio frequency standard causes the dual-comb mutual coherence to severely degrade. Specifically, traditional frequency comb stabilizes the carrier envelope offset at a radio frequency by a self-reference system, and the order number of each output comb tooth is over a hundred thousand. Thus, the phase noise of the radio frequency reference is significantly multiplied in output optical frequency by the same order of magnitude as the tooth order number. In this paper, we demonstrate an optical frequency linked dual-comb spectrometer where the two combs are locked to a common narrow linewidth laser. In this configuration, the two combs are synchronized at an identical optical frequency, which means that the carrier envelope offset of the two combs are changed to an optical frequency and the order number of the output comb teeth are reduced by two orders of magnitude. Therefore, not only the complex and costly self-reference system can be removed but also the phase noise of the optical frequency of each comb tooth is effectively reduced, which leads to lower mutual frequency jitters and better mutual coherence. To prove the performance, we measure the vl ＋ v3 P branch of 13C2H2 molecular and the results accord well with the reported line positions and reveals a spectral resolution of 0.086 cm^-1. The average signal-to-noise ratio exceeds 200 ： 1 （62.5 ms, 100 times on average） and the noise equivalent coefficient is 6.0 ×10^-6 cm-l.Hz-1/2. This work provides a solution for pragmatic dual-comb spectroscopy with high resolution and low-cost configuration.