Phase degradation of liquid crystal variable retarders and preconfiguring method for high-power continuous-wave laser

Abstract

The effects of laser-induced heat on the performance degradation of liquid crystal (LC) devices are critically important in applications involving laser systems. In this study, we investigated the influences of 1064-nm continuous-wave (CW) laser loading on an LC variable retarder (LCVR). The results show that thermal deposition initially causes an overall downward shift in the electronically controlled phase retardation curve. This phase retardation reduction is restored under a certain voltage and laser power by reducing the driving voltage. For common nematic LC wave plates that do not require voltage application, the decrease in phase retardation can be pre-compensated by increasing the corresponding LC cell thickness. For electrically controlled LC devices, the phase retardation under a high-power CW laser can be preconfigured by plotting phase response curves versus voltages at different laser powers. Based on these calibration curves, the LC devices can still service high-power CW lasers as long as the resulting temperature does not reach the clear point of the LC material. These results clarify the fundamental mechanisms of phase modulation variation induced by thermal deposition and could be useful for the fabrication optimization and effective implementation of LC devices in high-power laser systems.