Patterned photoresist spacers and photo-induced alignment coatings for liquid crystal waveplates and polarizers

The OMEGA laser system uses waveplates and polarizers to alter the polarization of the laser light. Both devices are formed using two glass substrates that contain alignment layers and are separated by vacuum-deposited thin-film spacers and filled with liquid crystals (LCs). Vacuum deposition of thin-film spacers is time-consuming and requires the use of expensive equipment. In this study, spacers were formed by photopatterning of a negative photoresist material using standard photolithographic techniques. These photoresist spacers are comparable to thin-film spacers in quality and are much easier to produce. A new non-contacting method for generating uniform LC alignment by irradiation of a linearly photopolymerizable polymer (ROLIC ROP-203/2CP) with polarized UV light was also investigated as an alternative to the current mechanical buffing process, which leaves particles and static charges on the substrate. This “photobuffing” process is easily scalable to large apertures. Because the application of photoresist spacers does not impact the laser damage threshold of the optics and the ROLIC photoalignment material has high laser induced damage resistance, both materials are feasible for use in the laser system.