Highly sensitive dispersion spectroscopy by probing the free spectral range of an optical cavity using dual-frequency modulation
Highly sensitive dispersion spectroscopy by probing the free spectral range of an optical cavity using dual-frequency modulation
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DOI：
10.1007/s00340-010-4120-9
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发表时间：
2010-11-01
影响因子：
2.1
通讯作者：
Axner, O.
中科院分区：
文献类型：
--
作者：
Schmidt, F. M.;Ma, W.;Axner, O.
双频调制（DFM）已被用于连续跟踪腔内气体的光学跃迁附近的光学腔模式的频移，用于评估气体浓度。给出了DFM色散谱（DFM-DS）信号的大小和线形的理论描述。由于信号是以射频的形式测量的，因此该技术对激光强度波动不敏感。信号强度仅取决于基本参数（包括谱线强度），可以通过曲线拟合精确获得，因此无需校准即可实现定量检测。在第一次演示中，使用基于窄带光纤激光器的紧凑装置，以6 Hz的分辨率测量了由于1531 nm附近的乙炔跃迁引起的379.9 MHz值附近的自由光谱范围的变化（即精度为10（8）中的1.5部分），其对应于3 × 10（-9）cm（-1）的最小可检测积分吸收（SNR=3）。
Dual-frequency modulation (DFM) has been used to continuously track the frequency shifts of optical cavity modes in the vicinity of an optical transition of a gas inside the cavity for assessment of the gas concentration. A theoretical description of the size and lineshape of the DFM dispersion spectroscopy (DFM-DS) signal is given. Since the signal is measured in terms of a radio frequency the technique is insensitive to laser intensity fluctuations. The signal strength, which can accurately be obtained by curve fitting, only depends on fundamental parameters (including the line strength), thus enabling quantitative detection without calibration procedure. In a first demonstration, using a compact setup based on a narrowband fiber laser, the change in free spectral range around a value of 379.9 MHz due to an acetylene transition near 1531 nm was measured with a resolution of 6 Hz (i.e. with an accuracy of 1.5 parts in 10(8)) in 12.5 s acquisition time, which corresponds to a minimum detectable integrated absorption (SNR=3) of 3x10(-9) cm(-1).