Tuneable and switchable liquid crystal laser protection system

The use of a liquid crystal Lyot filter as a simple and compact switchable laser protection system is demonstrated. The system OFF state exhibits a wavelength-independent transmission and switches to an ON state, which rejects a selected wavelength. The response time of the switchable system is <110  ms<110  ms, depending on the rejected wavelength, with the ability for faster switching of <5  ms<5  ms when using a lower-order rejection band. A rejection tuning range between 480 and 640 nm is demonstrated, and the potential to operate outside of the visible spectrum is discussed. In the ON state, the transmission at the rejected wavelength was found to be effectively limited by the polarizer extinction ratio, while transmission at other wavelengths allows for partial observations through the system even when in protection mode.