Analysis of adjusting effects of mounting force on frequency conversion of mounted nonlinear optics

Abstract

Motivated by the need to increase the second harmonic generation (SHG) efficiency of nonlinear optics with large apertures, a novel mounting configuration with active adjusting function on the SHG efficiency is proposed and mechanically and optically studied. The adjusting effects of the mounting force on the distortion and stress are analyzed by the finite element methods (FEM), as well as the contribution of the distortion and stress to the change in phase mismatch, and the SHG efficiency are theoretically stated. Further on, the SHG efficiency is calculated as a function of the mounting force. The changing trends of the distortion, stress, and the SHG efficiency with the varying mounting force are obtained, and the optimal ones are figured out. Moreover, the mechanism of the occurrence of the optimal values is studied and the adjusting strategy is put forward. Numerical results show the robust adjustment of the mounting force, as well as the effectiveness of the mounting configuration, in increasing the SHG efficiency.

Calculating the area of a particular deformation region of an optical surface based on the finite element method

“…To accommodate the propagation direction of the laser beam, the KDP crystal is mounted on a window-shaped aluminum frame and positioned obliquely at an angle of 45 degrees to gravity. The structural details of the mounting scheme have been described previously [35], and here we emphasize the key elements as follows. The KDP crystal is supported on the frame along the four edges of the bottom surface, and the periphery of the top surface is subjected to certain mounting force applied by squeezing the periphery with a number of thin plates compressed by some screws.…”

“…Note that there is no specific value of Young's modulus and Poisson's ratio for the KDP crystal, and the mechanical performance in terms of these two properties is expressed by the relationship between the stress and strain, as described below [35]…”

A two-parameter model for predicting thermal contact resistance between crystal and aluminum alloy based on turning morphology

“…The stress load in the KDP crystal module is usually less than 1.0 MPa. 4 Therefore, when the aluminum alloy with turning surface comes into contact with the KDP crystal, the peak of the aluminum alloy profile will contact the crystal surface, while the valley of the profile hardly contacts the crystal. On this basis, the model is simplified as shown in Figure 2(b) with the following assumptions:…”

“…3 Crystal and metal materials are usually clamped together in optical devices, and the crystal temperature sensors controlled by the heating source is installed on the metal. 4 Therefore, the thermal contact resistance (TCR) between the KDP crystal and metal material directly determines the temperature distribution in the crystal and the thermal-structural design of precision instruments.…”