Design And Tolerance Analysis Of Laser Guide Stars Launch System

Because of the turbulence caused by atmosphere,the observation of large ground-based telescopes is seriously restricted.Therefore,adaptive optics has been developed.In order to coordinate the AO(Adaptive Optics)system,laser guide star launch system has been developed to provide an artificial guide star.Most of the traditional laser guide star launch systems are designed according to the actual requirements,and there is no general structure and design scheme.Laser guide star launch system is laser delivery system,the influence of physical optical propagation is usually not considered,the design framework and optimization procedure are based on geometric optical propagation.A physical optical propagation modal is not established which will lead to the decline of the final performance.We first proposed a general structure of laser guide star launch system based on existing adaptive optics system,which consists of a beam expand system responsible for field coupling,a k-mirror system responsible for eliminating the effect of the earth rotation and a launch telescope responsible for the guide star launching.We first acquired a beam expand system with excellent performance after thermal analysis.Secondly,we provided an alignment design for k-mirror system after structure selection.As for launch telescope,we proposed a design method based on physical optics propagation.We first conducted the optics propagation module,then we constructed an initial design based on geometrical ray trace,finally we performed optimization based on physical optics evaluation criterion.The optimized design shows great performance which demonstrates the efficiency of our design method.After optimization process,we performed tolerance analysis on our design,tolerance allocation has been made and Monte-Carlo analysis has been performed.The design method proposed by us demonstrated that an optical design optimization procedure under geometrical optics evaluation criterion will not acquire an excellent physical propagation performance.The design method and tolerance method proposed in this paper will provide a good guidance for researchers to design similar laser propagation systems in the future.