宏-微脉冲激光激发钠信标回波光子数的数值计算与探讨∗

摘要

Sodium laser beacon (SLB) excited by a macro-micro pulse laser with low power has the following advantages: the return photons without fluctuations and the high merit quantity, although the laser beam propagation and the size of SLB suffer form the atmospheric turbulence. In addition, the macro-pulse profile may influence the interaction of laser and sodium atoms. For the macro-pulse with a Gaussian profile, it is useful to enhance the merit quantity and the excitation probability of the SLB to increase the width of micropulse. In order to obtain more of the return photons in the SLB, while increasing the laser power, the fine beam quality, the appropriate launch diameter, and the spectral width of the laser etc. must be considered. Therefore, it is of practical significance for the SLB with fine characteristics to optimize the laser parameters, the launch diameter and launch pattern.%当采用低功率的宏-微脉冲激光激发钠信标时，尽管激光传输和钠信标光斑大小受到大气湍流影响，但是钠信标具有回波光子数无起伏且激发品质因数高的优点。除此之外，宏-微脉冲激光激发钠信标还与激光的宏脉冲线型有关。对于高斯线型的宏脉冲，增大微脉冲的宽度有利于提高激发钠信标的品质因数和激发态概率。为了获得更多的钠信标回波光子和较小的钠信标半径，增大激光功率的同时要考虑良好的光束质量、适当的激光发射口径以及光谱宽度等影响因素。因此，优选宏-微脉冲激光的参数、发射口径、发射方式等对于激发优良特性的钠信标有着重要的现实意义。