不同波前振幅分布对于斯特列尔比的影响

Influence of different wavefront amplitude on Strehl Ratio

斯特列尔比SR(StrehlRatio)是衡量一个光学系统光能强度分布优劣的重要评价指标。本文根据激光核聚变中利用修正SR模型,数学推导研究得出了波前位相及振幅信息,获取最大的SR比的两者匹配条件:即斯特列尔比与波前振幅分布和波前位相的指数函数分布的一致性成正比关系。并对该结论进行了计算机仿真验证。实验根据一有象差波面位相与一组不同的振幅分布函数进行匹配计算:当给定波前位相分布(PV<1λ)时,则不同的振幅分布得到的斯特列尔比从0.92-0.99之间变化。实验结果表明当波前振幅分布与波前位相的指数函数分布一致性越好,系统斯特列尔比越大,并且斯特列尔比主要由波前位相分布决定。该结论说明:虽然激光核聚变中振幅是高阶超高斯型分布的平顶光束,只有当波前位相的均方根趋于零相当于一平面波时则其指数分布与振幅分布达到了好的一致性,才能得到高的SR比。

SR （Strehl Ratio） is an important parameter to evaluate the optical intensity distribution of an optical system. This paper describes the best matching coherence to the wavefront phase with different amplitude distribution based on a corrected SR formula, namely SR is proportional to the coherence of the amplitude distribution with the exponent function of wavefront phase. The conclusion is validated through computer simulations by calculating the SR of a wavefront phase with aberration and a group of different amplitude distribution. SR value mainly depends on phase distribution, and different amplitude distribution can affect SR value from 0.92 to 0.99 at the given phase distribution（PV〈1λ ）. The simulations prove that SR is proportional to the coherence of amplitude distribution as the exponent function of wavefront phase. The result shows that although the amplitude distribution is a flat top beam of super- Gauss with high order power in ICF （Inertial Confinement Fusion）, only when RMS of the wavefront phase tends to zero approaching to a plane wavefont, that is to say coherence of the amplitude distribution with an exponent function of wavefront phase with better SR can be obtained.