Study On The Design And Process Of Phase-type Soft-edge Aperture

At the moment,ICF(Inertial Confinement Fusion)is one of the most promising options to solve the energy problem.It uses the laser as the driving source to continuously transmit and amplify the laser,and has strict requirements on the quality of the laser beam.The intensity disturbance caused by the Fresnel diffraction modulation during transmission will make the occurrence of small-scale self-focusing in the amplification system,thereby reducing the flux of system and destroying the system components.At present,soft-edge aperture is effectively used to solve the problems above and reduce the system cost.Based on the premise of suppressing the diffraction modulation,the phase-type soft-edge aperture is designed in this paper.So a series of research study is carried out around the selection on the methods of the structure of the soft-edge aperture,the evaluation functions,the parameters affecting the performance of the soft-edge aperture in the design process,and the process of the soft-edge aperture.The main contents are described in detail as follows:1.The background of the soft-edge aperture and the current research status of related elements on controlling the beam quality at home and abroad are introduced.Then the scalar diffraction theory,error diffusion method,two-phase coding principle,GA(Genetic Algorithm)and the structure parameters and phase modulation principle of LCOS spatial light modulator in the process of aperture design and simulation are analyzed in detail.2.The change of filling factor under different soft-edge factors and different Fresnel numbers is discussed,which provides a basis for the selection of parameters(mainly super-Gaussian order)of phase type soft-edge aperture and a theoretical model for programming.3.In view of the shortcoming of the single-sided surface optimization of the soft-edge aperture designed by the error diffusion method and the two-phase encoding,GA(Genetic Algorithm)using the root mean square error function as the evaluation function is proposed to optimize the image surface and defocusing surface at the same time.The phase-type aperture with soft factor of 0.1 is designed and the error of the design result is small(1.33%?2.58%).In addition,the influence of different pixel size and different filter hole size on the evaluation function value is discussed.4.The same phase distribution as the soft-edge aperture is designed for experiment according to the principle of LCOS phase modulation.The experimental results verify the consistency between the soft-edge factor(0.103)under the design results and the target soft-edge factor(0.1),and determine the feasibility of the current method.5.Two-phase and four-phase soft-edge apertures are fabricated by using UV exposure and RIBE technology,then the distribution of beam intensity under the current process is tested by experiment.The experimental results verify the consistency between the soft-edge factor(0.099,0.095)under the design results and the target soft-edge factor(0.1).Finally,the influence of etching depth error and alignment error on the evaluation function value is analyzed theoretically.