动态聚焦中小焦斑的波前判据

Wavefront criterion of small focal spot in optical zooming

在直接驱动中,由于靶丸在内爆过程中不断压缩变小,激光束的初始焦斑与压缩后的靶丸不再匹配,导致能量从靶丸边缘流失.光学动态聚焦是指在靶丸压缩变小的过程中,动态减小辐照焦斑的尺寸,这对提高光束与靶丸的耦合效率有着非常重要的意义.靶丸压缩后期小焦斑的实现条件是解决光学动态聚焦的首要问题.根据光的全频段传输规律,本文采用构造低频和中高频波前畸变源的方法,在不同目标焦斑的束匀滑条件下,分别给出了小焦斑尺寸与低频波前、中高频波前的定标关系,作为小焦斑实现方式的波前判据.根据波前判据即可找出要实现不同的小焦斑需对低频和中高频波前畸变矫正控制的范围.

In the direct drive, since the target is becoming smaller in compression process, the initial focal spot will no longer match the compressed target, leading to large losses of energy from target edge. Optical zooming means making the focal spot smaller when the target compresses. In this way, the coupling efficiency between the beam and target can be improved. It has great significance. The primary problem of solving the optical zooming is the qualification of small focal spot. According to the full-band optical transmission rules, in this paper constructed are low and medium-high frequency wavefront distortion sources under different smoothing conditions, and then given is a scaling relation between wavefront and focal spot size. The scaling relation can be regarded as a wavefront criterion of small focal spot. Using this wavefront criterion, the correction range of low and medium-high frequency wavefront distortion can be known to achieve a small focal spot.