Optomechanical analysis and performance optimization of large-aperture KDP frequency converter

Abstract Surface characteristics of large-aperture potassium dihydrogen phosphate (KDP) frequency converter have direct and significant impacts on the performance of high-power solid-state laser in Inertial Confinement Fusion (ICF) facility. In this study, we analyze the close relationships between the phase gradient and the optical performances including type-I phase matching capacity and focusability of KDP frequency converter theoretically. Moreover, the influences of external forces are studied with field interferometry and finite element method (FEM). An edge-adaptive clamping apparatus with two-stage preload controllers (TSPCs) is proposed to mitigate the gravitational effect. With the proposed integrated optomechanical method and principle verification experiment, new clamping method is proved to be effective to perform offline precision calibration, improve frequency conversion efficiency and has potential for use in online surface control of this large-aperture transmission optics. The coupled effects of preload and gravity on optical performance are analyzed for identifying the characteristics of new clamping method, and the optimal preloads at typical installation attitudes are determined.