Truong Gar-Wing, Waxman Eleanor M, Cossel Kevin C, Baumann Esther, Klose Andrew, Giorgetta Fabrizio R, Swann William C, Newbury Nathan R, Coddington Ian
Opt Express. 2016 Dec 26;24(26):30495-30504. doi: 10.1364/OE.24.030495.
We describe a dual-comb spectrometer that can operate independently of laboratory-based rf and optical frequency references but is nevertheless capable of ultra-high spectral resolution, high SNR, and frequency-accurate spectral measurements. The instrument is based on a "bootstrapped" frequency referencing scheme in which short-term optical phase coherence between combs is attained by referencing each to a free-running diode laser, whilst high frequency resolution and long-term accuracy is derived from a stable quartz oscillator. The sensitivity, stability and accuracy of this spectrometer were characterized using a multipass cell. We demonstrate comb-resolved spectra spanning from 140 THz (2.14 µm, 4670 cm) to 184 THz (1.63 µm, 6140 cm) in the near infrared with a frequency sampling of 200 MHz (0.0067 cm) and ~1 MHz frequency accuracy. High resolution spectra of water and carbon dioxide transitions at 1.77 µm, 1.96 µm and 2.06 µm show that the molecular transmission acquired with this system operating in the field-mode did not deviate from those measured when it was referenced to a maser and cavity-stabilized laser to within 5.6 × 10. When optimized for carbon dioxide quantification at 1.60 µm, a sensitivity of 2.8 ppm-km at 1 s integration time, improving to 0.10 ppm-km at 13 minutes of integration time was achieved.
我们描述了一种双梳状光谱仪，它可以独立于基于实验室的射频和光学频率参考运行，但仍能够实现超高光谱分辨率、高信噪比和频率精确的光谱测量。该仪器基于一种“自举”频率参考方案，其中通过将每个梳状信号参考到一个自由运行的二极管激光器来实现梳状信号之间的短期光学相位相干，而高频分辨率和长期精度则来自于一个稳定的石英振荡器。使用多程池对该光谱仪的灵敏度、稳定性和准确性进行了表征。我们展示了在近红外波段从140太赫兹（2.14微米，4670厘米）到184太赫兹（1.63微米，6140厘米）的梳状分辨光谱，频率采样为200兆赫兹（0.0067厘米），频率精度约为1兆赫兹。在1.77微米、1.96微米和2.06微米处水和二氧化碳跃迁的高分辨率光谱表明，该系统在现场模式下获取的分子透射率与参考微波激射器和腔稳定激光器测量时的结果偏差不超过5.6×10。当针对1.60微米处的二氧化碳定量进行优化时，在1秒积分时间内灵敏度为2.8 ppm - 千米，在13分钟积分时间内提高到0.10 ppm - 千米。
