Preliminary Investigation into the Effects of High-Power Illumination on Optical Phased Arrays

摘要

The phase-vs.-voltage characteristics of liquid-crystal phase retarders and optical phased arrays (OPAs) were measured while the devices were exposed to high-power-CW-laser radiation at 1.08 micrometers. The results indicate that as the applied CW power is increased, the available phase- modulation depth of the devices is reduced, presumably due to heating. In addition, transient experiments where the high-power laser was turned on and off indicate that the particular liquid crystal on silicon (LCoS) OPAs we examined have a thermal time constant of around 20 seconds. Microscopic examination of the liquid-crystal devices indicates that there is no apparent damage to the bulk materials used in the device, although most of the devices appear to have suffered from liquid-crystal migration that is presumably due to thermal expansion and contraction.