The Study Of Edge-driving Deformable Mirror Used For Compensating Low Order Aberration

With the constant improvement of the laser output beam power,control of the big stroke low-order aberration becomes one of the key difficulties that the high power laser beam control system faces.Now the idea of "multiple correction" is properly popular in the control of beam quality,using the multiple discrete-driving deformable mirror.The problem of multi-level control-coupling existing in this technical makes the system more complex,and the "printing through effect" produced by the irradiation of light induces more high-order aberration.All of those will enlarge the complexity of beam quality control in the system.Without the printed through effect,the edge-driving deformable mirror has the characteristics of large stroke of compensation,and can compensate a large number of low order aberrations in the system via simple solution,therefore,reduce the complexity of the beam control system.From the perspective of the thin plate theory based on Love-Kirchhoff assumption,the paper has provided the whole load balance equations satisfied by deformation displacement of the disc mirror surface in the Z direction and the overall load when the disc receives overall load.Meanwhile,it has thoroughly analyzed the integral equation between the net shear force and the bending moment and size of the loading force by the 24 load points,when the mirror generates two kinds of surface shape,defocus and astigmatism,providing the theory basis and the initial structure parameters for the optimization design of deformable mirror.This paper puts forward the structure innovation of the edge-driving deformable mirror.After analyzing 24 forces calculated from thin plate theory,original 12 arms and 24 forces mirror is simplified to a 4 arms and 4 forces mirror.Based on the relation between the net shear force and the bending moment and size of the loading force when the mirror generates two kinds of surface shape,defocus and astigmatism,the article has proposed the design of side surface ladder shape driving arm,resulting in a improvement of the accuracy of the defocus surface shape from 33.3% to 3.7%(The ratio of residual face PV value and the generated face PV value).By adopting the neck structure,four arm edgedriving deformable mirror's defocus PV value has increased from 1.68?m to 6.13 ?m,and the astigmatism PV value has increased from 2.96?m to 5.52?m.On this basis,the optimal structure parameters of the edge-driving deformable mirror is obtained through optimization of structural mechanics simulation program.This is the first domestic launched production and testing of the four arm edge-driving deformable mirror,successfully having formed the production process,and completed its calibration and influence function's measurement.The actual measurement via a ZYGO interferometer.shows that,in this paper,within 50 mm effective diameter,the largest defocus PV value which the four arm edge-driving deformable mirrors can generate is 12.83?,and the largest 90°astigmatism PV value is 11.89?.The fitting residual error of two kinds of surface shape were 2.04 ? and 1.70?,respectively.