Liquid Crystal Beam Shaping Devices Incorporating Coumarin-Based Photoalignment Layers

1. Abstract Liquid crystal (LC) devices incorporating photosensitive polymers based on coumarin were investigated for laser beam shaping applications. Presently, the OMEGA EP laser system uses pixelated metal beam shaping devices, though their relatively low damage threshold (approximately 0.2 J/cm 2) makes them poor options for long-term usage. LC devices have the major advantages of a much higher damage threshold (9-18 J/cm 2). Previously, 10 μm pixelated LC beam shapers were fabricated by patterning a commercially available cinnamate-based photopolymerizable LC alignment material (ROLIC) through a mask using polarized UV light to control the LCs' orientation. This project investigated fabrication and characterization of LC beam shaping devices employing a coumarin-based linearly photopolymerizable polymer (LPP) as an alternative to the cinnamate-based LPP. After developing an experimental procedure for creating coumarin-based LPP liquid crystal cells, analyzing cell transmission data, and evaluating LPP coating uniformity, it was determined that the coumarin-based LPP could be photolithographically patterned. However, more research is needed to improve coating uniformity and determine the UV irradiation conditions necessary to improve pixel resolution.