Abstract

Filters for use at 45 degrees made with classical quarter wave stacks and (multiple ) half waves exhibit a large degree of polarization. The P- polarized component has a much wider bandwidth than the S- polarized component. The wavelengths for each polarization are typically not coincident and the average transmission does not yield a suitable passband. Thelen¹,² has suggested methods of reducing polarization that introduce non-quarter wave layers and / or third materials and many layers in order to provide a non-polarizing edge filter. Baumeister³ designed bandpasses with 3 or more materials also. Either of these complications is difficult to deal with. Stress from too many layers and monitoring of non-quarter wave layers are both undesirable. Here it is shown how layers that are multiples of quarter-waves at normal incidence can be used to design filters with very low polarization at severe angles. The polarization for this new design is larger than for the above referenced filter types, but it is much simpler to build.

© 1998 Optical Society of America