Polarization Control by Deep Ultra Violet Wire Grid Polarizers
Polarization is an inherent property of transversal electromagnetic light waves. Hence, the control of the polarization state is a fundamental requirement in many optical applications. Nowadays, optical measurement and fabrication technology strive to shorter wavelengths in the ultra violet to benefit from larger resolution and material specific electronic transitions used for analysis. Thanks to the progress of nano-technology it has become feasible to manufacture subwavelength devices such as wire grid polarizers for this wavelength regime. These elements offer a very large acceptance angle, large areas and can be integrated with other optical elements such as photo masks or image sensors. However, not only geometrical properties must be met, but also specific materials properties must be provided. In this chapter the principle concepts of polarizers basing on birefringence, reflection and dichroism are very briefly explained and their limitations are discussed. An overview of commercially available elements is given to set wire grid polarizer in a bigger picture and the characterization of polarizing elements is described. Further the working principle, structural and material requirements for wire grid polarizer are discussed in detail. The fabrication and design is presented. The transmittance spectra of fabricated elements exhibit resonances in the near ultra violet spectral region. It is discussed how these can be utilized to reconstruct the geometry and deduce the performance of the polarizers at much shorter, less accessible, wavelengths in the far ultra violet. Finally, a comparison of different materials for wire grid polarizers in the ultra violet wavelength range is presented.