Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA.
J Phys Chem A. 2011 Sep 1;115(34):9411-21. doi: 10.1021/jp111177c. Epub 2011 Jul 26.
The averaged transmitted intensity of a cavity excited by a linearly frequency swept laser with finite line width is derived and presented as a sum over passes, analytical integrals (where the sum of passes is converted to a continuous time variable), and an approximate but computationally more stable stationary phase approximation expression. The transmitted waveform is used to derive the bias in extraction of the cavity decay rate from such a cavity transient for three different fitting models. Numerical simulation of cavity excitation gives statistical fluctuations in the transmitted intensity that leads to noise in the cavity decay rate. For a range of parameters spanning those likely to be encountered in real experiments, numerical results are presented. These demonstrate that the theoretical signal-to-noise ratio and thus sensitivity of swept cavity (or equivalently, frequency) CRDS is substantially below that for CRDS where one attenuates the laser either with current modulation or with an external modulator.
推导了有限线宽线性频率扫描激光激励腔的平均透射强度，并将其表示为通过次数的和、解析积分（其中通过次数的和转换为连续时间变量）和近似但计算上更稳定的定相近似表达式。透射波形用于从这种腔瞬态中提取腔衰减率，针对三种不同的拟合模型，得到了偏置。对腔激励的数值模拟导致了透射强度的统计波动，从而导致腔衰减率的噪声。对于跨越实际实验中可能遇到的参数范围的参数，给出了数值结果。这些结果表明，理论上的信噪比，因此扫频腔（或等效地，频率）CRDS 的灵敏度大大低于通过电流调制或外部调制器来衰减激光的 CRDS 的灵敏度。
