准直脉冲激光大气传输热晕数值分析  

Numerical Analysis on Thermal Blooming of Collimated Pulsed Laser Beams Propagating in the Atmosphere

作　　者：孙中涛[1] 孙晓泉[1] 李晓星[1] 

机构地区：[1]合肥电子工程学院,安徽合肥230037

出　　处：《光电技术应用》2006年第3期24-27,72,共5页Electro-Optic Technology Application

摘　　要：大气通道上介质对激光部分能量的吸收,导致大气折射率的改变,形成自散焦负透镜,产生热晕.使激光发生畸变,限制了激光能量在大气中的有效传输.以准直脉冲高斯激光束大气传输为例,数值分析了热晕对由光束的声传递时间(即流体动力学时间)定义的两种脉冲长、短脉冲大气传输的影响:长脉冲受到非线性热晕效应影响很大,光束截面上光强发生了重新分布,轴上光强凹陷,峰值光强向周围扩展;短脉冲主要受到线性吸收的作用,受到的非线性热晕效应影响很小.提出了采用脉冲间隔适当的序列短脉冲传输来提高激光传输能量的方法.Propagation of a collimated, pulsed laser Gaussian beam in an absorbing medium has been investigated theoretically. The energy absorbed by the medium of the propagation path causes heating, leading to an index of refraction change that causes self-defocusing, which induces thermal blooming. Thermal-blooming effects can limit the laser power that can be effectively propagated through the atmosphere. Numerical results for pulsed laser Gaussian beams are presented in form of irradiance profiles as functions of range. The pulse time is of the order of the hydrodynamic time, i.e. , the time required for a signal traveling at the sonic velocity to cross the beam. The long laser pulse is subjected to thermal blooming more than the short laser pulse, which is mainly subjected to the linear absorption. An initial Gaussian beam distribution is deformed into the dimple near the center with the peak irradiance near the edge of the beam. Finally, an approach adopting repetitively pulsed laser with optimized intervals between pulses is put forward, by which high average power can be transmitted.

关 键 词：大气传输 脉冲激光 热晕 数值分析 

分 类 号：TN24[电子电信—物理电子学]