ABSTRACT
We have already seen in Chapter 2 that the characteristics of coatings change when they are tilted with respct to the incident illumination, and the degree of change depends on the angle of incidence. We have also studied the shifts that are induced in narrowband filters. Narrowband filters are a simple case because the tilt angle is usually small, and we can assume that the major effect is in the phase thickness of the layers, which is equally affected for each plane of polarization. For larger tilts, however, the admittances are also affected, and then the performance for each plane of polarization differs. Some important applications take advantage of the difference in the performance between one plane and the other, which can be controlled to some extent, making the construction of phase retarders and polarizers possible. On the other hand, the differences in performance can create problems, and although it is impossible to completely cancel the effects, there are ways of modifying it so that a more acceptable performance may be achieved. With purely dielectric layers, tilting is certainly a complication, but when metal layers are added, the behavior is still more complicated and can even be rather strange. In this chapter, therefore, we concentrate on the dielectric case. Metals will be included in the following chapter.
