摘要
由于大气通道上介质对激光能量的吸收,改变了大气折射率,形成自散焦负透镜,从而产生热晕。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。以准直高斯光束为例,模拟单脉冲和序列脉冲激光大气传输,对均匀风场和无风两种情况下激光在不同靶程光束截面的光强分布进行了数值分析。结果表明:长脉冲比短脉冲受到非线性热晕效应影响大;序列脉冲存在一个最优化脉冲间隔,使上靶光强存在20%～30%的涨幅。最后,在没有采用自适应光学系统对畸变进行补偿的情况下,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 trains of short-duration and single pulsed laser Gaussian beam in an absorbing medium has been investigated numerically. The energy absorbed by the medium of the propagation path causes heating, leading to refraction index change that causes self-defocusing, which induces thermal blooming. Thermal blooming effects can limit the laser powers which can be effectively propagated through the atmosphere. Results for two kinds of pulsed laser Gaussian beams are presented in form of irradiance profiles as functions of range for different propagation condition, such as different laser energy, propagation distance, wind velocity, interval between pulses. It is found that the long laser pulse is subjected to thermal blooming more than the short laser pulse. For trains of short-duration pulsed laser, over a certain range of pulse repetition rate, the beam distortion is not only minimized, but the peak intensity is actually enhanced about 20%-30% over the undistorted value. Enhancement depends on the degree of pulse overlap and is most evident for a collimated beam in a uniform wind. Finally, at the condition without adaptive optics system, an approach is put forward which can transmit high average power by using repetitively pulsed laser if the intervals between pulses are optimized.
出处
《红外与激光工程》
EI
CSCD
北大核心
2007年第2期189-193,共5页
Infrared and Laser Engineering
基金
国家自然科学基金重点资助项目(50534050)
关键词
大气传输
热晕
脉冲序列
高斯光束
理论分析
Propagation in atmosphere
Thermal blooming
Trains of short-duration
Gaussian beam
Theoretical analysis
