Compensation Of Low Order Aberrations Based On The Cylindrical Deformable Mirror

The slab lasers is one of the most potential construction to obtain both high average and peak power laser.However,there are always large low-order aberrations in the high power laser wavefront because of the thermal effect such as the thermal lens,thermoinduced birefringence and non-uniform distribution of the pump light.The peak to valley(PV)value of thermally induced wavefront distortion can be dozens of microns,and it's difficult to be corrected by a single deformable mirror with limited correction range.According to this,the low-order aberration compensation of the slab lasers has important practical significance and broad future.In this thesis,we investigated the low-order aberration compensation of slab lasers by building a reflective low-order aberration compensation system.To begin with,the low-order aberration compensation is studied based on active beam shaper.The low-order aberration compensate capability is analyzed by the matrix model of a reflective beam shaper with tunable layout parameters.Adjustments are calculated directly from Zernike coefficients on the output plane according to concise formulas.The effectiveness of this method and the precision of the formulas are verified by a series of experiments with a laboratorial close-loop compensation system.Besides,the design and fabricating of cylindrical deformable mirror(CDM)is studied.Here we present the concept of compensate low-order aberration by CDM.The possible implements of CDM are analyzed according to the mechanical formulas.The results show that it's the more proper to made CDM by applying concentrated loading on the edge of a wide beam.The construction of CDM based on the flexible hinge is designed and the parameters are optimized by FEA method.A prototype of CDM is fabricated.The test results show that the PV of deformation achieved 15?m and PV of residuals is smaller than 0.6?m.Finally,the compensate capability of CDM is studied by experiments.A close-loop compensate system with CDM is built and a series of experiments are done for different low-order aberrations.The effectiveness of this method is proved by experiment results.After compensation,the low-order component of residuals is very small,the high-order component is depend on the fabricating accuracy of CDM surface.