Influence Of Actuator Arrangements On Low-Frequency Phase Fitting Capability Of Deformable Mirror

In the Inertial Confinement Fusion (ICF) system, stringent shapes and energy distributions of the focused spot is desired for physical experiments. The characteristics of the focused spot is decided by the beam quality of laser beam that enter the focusing elements finally, which is affected by the phase distortion introduced in the entire transmission of the beam. Therefore, the correction of phase distortion has great significance on the focused beam, and the low-frequency phase of phase distortion determines the main lobe of focal spot. Adaptive optics method can effectively correct the low-frequency phase, providing a feasible way to solve the focal spot smoothing of ICF. Based on the least squares method and numerical simulation by MATLAB, the fitting ability of continuous surface deformable mirror (DM) with discrete drive to the low-frequency phase distortion has been studied in this paper. Its main contents is summarized as follows:1. Based on the least-squares method, considering the random perturbations to the drive device of DM, we have studied the influence of the number of actuators, the arrangements, the coupling coefficient and the spatial scales of low-frequency phase on the anti-disturbance ability. The results show that the anti-disturbance ability of DM with square-array actuators is better than triangular-array ones; the larger coupling coefficient of DM, the greater anti-disturbance ability of which; the anti-disturbance ability of DM is proportional to the density of drive device, all of which provides some guidelines for designing DM.2. Based on the combinational deformable mirror (CDM) method, we have studied the impact of different combinations of DM on the fitting ability of low-frequency phase. The numerical simulation results show that by changing the different combinations of two DMs, the fitting ability of CDM is better than any single DM; by optimizing the coupling coefficient and Gaussian index of influence function of DM, the fitting ability of DM can be effectively improved. For a CDM with two DMs that have64units each, if coupling coefficient is less or greater than0.65, we get the best fitting effect when Gaussian index is equal to2or4, respectively. The CDM can break through the limit of existing manufacturing level of DM, achieving the increase of effective correction stroke of DM and the density of drive device with the same effective aperture.