超短脉冲厄米-高斯光束在湍流大气中的光谱移动和光谱跃变

Spectral shift and spectral transition of ultrashort pulsed Hermite-Gaussian beams in the turbulent atmosphere

基于广义惠更斯-菲涅尔原理,推导出了超短脉冲厄米-高斯(H-G)光束在湍流大气中的光谱传输方程,研究了其光谱移动和光谱跃变特性,并给予了合理的物理解释.研究表明,超短脉冲H-G光束通过湍流大气传输其光谱特性由大气折射率结构常数、厄米多项式阶数、脉冲宽度和观察点位置坐标等因素共同决定.轴上点光谱为蓝移,随着离轴距离的增大,光谱由蓝移变为红移,无光谱移动点的位置坐标与脉冲宽度无关.此外,当湍流增强到一定程度时离轴点还存在光谱跃变现象.自由空间与湍流大气中的光谱跃变行为存在很大的差异,本文对此进行了详细的分析.

Based on the extended Huygens-Fresnel principle, the analytical expression for the spectrum of ultrashort pulsed Hermite- Gaussian （H-G） beams propagating through the turbulent atmosphere is derived. The spectral shift and spectral transition are studied, and reasonable physical explanations are given. It is shown that the spectrum depends on the structure constant of the refractive index, order of the Hermite polynomial, pulse duration and position of the observation point. The on-axis spectrum is blue-shifted, the off-axis spectrum becomes red-shifted with increasing transverse coordinate, and the position with null spectral shift is independent of pulse duration. Furthermore, there exists an off-axis spectral transition when the turbulence reaches a certain degree. The behavior of the off-axis spectral transition in turbulence is very different from that in free space, which is analyzed in detail.