McCaul B W
Appl Opt. 1970 Mar 1;9(3):653-63. doi: 10.1364/AO.9.000653.
The plasma electrons in pulsed far ir lasers constitute a temporary divergent refractive element. This lens element can be strong enough to prohibit stable laser modes and serves to explain the delay commonly reported between current and laser pulses. With electron recombination the cavity rapidly becomes stable, Q switching the laser pulse. The lens effect and Q-switching rate are calculated in terms of tube dimensions, laser frequency, electron density, and radial electron density distribution. Higher laser frequencies appear earlier when this effect is operative. A simple criterion is given to distinguish this delay effect from other sources of laser pulse delay. Experimental measurements are presented of cavity stability as a function of mirror curvature and electron density; wall reflections are shown to be important. The radial electron density distribution is compared with plasma theory results. Lens effects associated with the laser gain are shown to be negligible.
脉冲远红外激光器中的等离子体电子构成了一个临时的发散折射元件。这个透镜元件的强度足以禁止稳定的激光模式，并用于解释通常报道的电流脉冲和激光脉冲之间的延迟。随着电子复合，腔迅速变得稳定，从而对激光脉冲进行调Q。根据管子尺寸、激光频率、电子密度和径向电子密度分布计算了透镜效应和调Q速率。当这种效应起作用时，较高的激光频率会更早出现。给出了一个简单的标准来区分这种延迟效应与激光脉冲延迟的其他来源。给出了作为镜曲率和电子密度函数的腔稳定性的实验测量结果；壁反射被证明是重要的。将径向电子密度分布与等离子体理论结果进行了比较。与激光增益相关的透镜效应被证明可以忽略不计。
