Research On The Structural Misalignment, Optimization, And Zoom Technology Of Laser Beam Expanders

Laser beam launching systems are widely used in the areas of target trackingand laser communication in which a variety of new challenges, such as workingtemperature and target’s distance variations, are arising. Based on these problems,aiming at improving the beam’s far field performance, some explorations on theoptomechanical analysis and laser beam expander design methods were carried outin this dissertation.Firstly, rules of optical system transforming the laser beams, aberration theory,and beam propagation algorithms et al, are mathematical tools to evaluate thebeam’s far field performance. Thereby, these contents were summarized initially,assisting in analyzing the impact of several typical wavefront aberrations on beams.And then, the misalignment model was established and subsequently furthergeneralized by means of homogeneous transformation.Secondly, a novel approach for thermal-optomechanical coupling analysis wasproposed. By using secondary development techniques, optical system’smisalignment model was integrated into the finite element analysis within whichthere are a number of sophisticated structural optimization algorithms. Differentfrom the traditional integrated analysis, this method made the purpose of effectivelyoptimizing the mechanical structure for an optimally optical performance feasible.As an example, the wavefront aberration of a beam expander was successfully reduced nearly by3/4times compared with bracing structure not optimized within arange of±50℃, that is, it achieved an almost ideally emitting beam. And theoptimized bracing structure was easily fabricated with one kind of conventionalmaterial, HT200, and without flexible elements and composite materials.Finally, a creative switching zoom scheme for laser beam expanders, as well asits special alignment program, was proposed. Through combining the geometricaland physical optics in optical optimization, in the form of sharing one main mirrorand switching different secondary working mirrors, a zoom off-axis reflective beamexpander was designed. This expander is available to switch its expanded ratio from1.5to1.8, keeping the two emitting beams’ central positions and directions as thesame. The simulation and adjustment experiment results both validated the designand set the foundation for the applications of laser zoom launching systems.