Polarization Components for the UV Range

Abstract

Optical polarization components are used in numerous applications that include photography, liquid crystal displays, polarimetry, astronomy, defense, sensing and photolithography, to name just a few. There are many types of polarizers and polarization components currently available. Polarizers based on metal wires, birefringence in crystals and on specially designed dielectric multilayers are among the widest spread (although the variety of known polarizers is by no means limited to these technologies). While polarizers oriented for the visible and near IR wavelengths ranges perform well, that is not the situation in the UV, especially for deep and far UV. For example, inexpensive plastic polarizers are not useable at UV wavelengths since the plastics are not sufficiently transparent. The high-end UV polarizers (such as those based on birefringence (Glan-Thompson) or on multilayers (cube beam-splitters)) are more expensive than the same types designed for the visible and near IR range. In addition, their performance degrades substantially at the shorter wavelengths of light. For example, deep UV polarizers designed to work at 248 nm offer an extinction of just 100–1000, compared to 10⁵ for visible polarizers, but demand a high price even for a small working area. In addition, the performance of almost all current types of polarizers capable of performing at deep UV and shorter wavelengths are strongly dependent on the angle of incidence of light on the polarizer. For example, tilting the incident light beam away from normalincidence, the extinction degrades considerably and/or the preferred polarization may rotate. Far UV polarizers are available only by special order, are extremely expensive, and offer fairly poor performance compared to polarizers for the visible spectrum.