Polarization Optics

Abstract

Physics of wide variety of polarization components and techniques available on the market is explained and summarized in six sections with details that cannot be found in textbooks or primers. The chapter opens with classification of polarizers, introducing basic parameters: extinction ratio and transmission. Brief insight into design and appropriate clamping technology of the simplest types of polarizers—the sheet and dichroic polarizers—precedes the discussion of much more sophisticated crystal polarizers. Significant portion of mathematics needed for understanding theory of beam propagation in birefringent media is dispatched to Chap. 12, leaving only phenomenological explanation based on the Huygens principle. Table 5.2 in this section presents the fullest summary of crystal polarizers—Nicol, Foucault, Glan-Taylor (Glan-laser), Glan-Thompson, Glan-Taylor (Brewster angle)—and separating prisms—Wollaston, Nomarski, Rochon. Birefringence is explained using the concept of ellipsoid of refractive indices, and practical geometrical technique of finding propagation direction for the extraordinary ray is presented. Numerous practical aspects that determine efficiency of a particular polarizer are discussed, and real comparative measurements of the three basic types of polarizers are summarized in Table 5.3. Section 5.2 analyzes polarization separators: beam-splitting cubes of various types and Nomarski prism. The Nomarski prism is a very tricky element, often being explained erroneously, therefore this section may serve as a good introduction into the subject, supported also by detailed mathematics and Fortran codes in Chap. 12. The subject of Sect. 5.3—phase elements—requires mathematics of a complex variable, especially the Fresnel rhomb and its modifications. Some simple but detailed analytical computations are also needed to realize spectral limitations of phase elements. However, this portion of analysis arms the reader with valuable practical ability to discriminate between right and wrong use of waveplates and understanding of some practical tricks like their tilting. Compensators—the Babinet-Soleil and quarter-wave plate—is the topic of the forth section. The figures in this section are mostly self-explanatory. Polarization isolators are the essential part of many delicate optical experiments, and therefore Sect. 5.5 sheds some additional light on this subject that cannot be learned from textbooks because many ideas were developed and brought to market only recently, like broadband Faraday isolators or polarization-independent isolators. Section 5.6 of this chapter presents a useful practical example of using polarization components to create simple variable attenuator.

When you need to care about polarization: interferometry, heterodyning, optical isolation, variable attenuation.