Pulsed Laser Written Diffraction Gratings in Liquid Crystal Polymers

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Abstract
In this work the writing of diffraction gratings in liquid crystal polymer films is studied, where the exposure mechanism is thermal and takes the material from an opaque to a transparent state. A pulsed ruby laser is used to write gratings and the evolution of diffraction is monitored using a continuous wave laser. The resulting diffraction efficiency is compared with an analytic theory for a range of laser pulse energies and grating spacings. Results from the comparison are very good, and final efficiencies of around 5% are obtained, which is near the theoretical maximum for the material used.