This book covers the basic concepts and methods involved in polarization of light, and features important methods of analysis such as Jones matrices, Stokes parameters, and Poincaré sphere. It provides the background needed to understand the workings of, and to design, various photonic devices, including Faraday rotators, inline fiber optic components such as polarizers, wave plates, and polarization controllers, and polarimetric sensors such as fiber optic current sensors. Birefringence and the phenomenon of polarization mode dispersion (PMD) in single-mode fibers are also covered. The discussion of concepts is succinct, and the presentation of methods includes concrete examples, making the book an ideal text for students and a useful resource for engineers.

The polarization phenomena associated with light waves are extremely important in many areas of photonics. Many important polarization-based devices have been developed, including Faraday rotators; in-line fiber optic components, such as polarizers, wave plates, and polarization controllers; and sensors, such as fiber optic current sensors, and fiber optic gyroscopes. In order to understand the workings of such photonic devices and to improve their design, sound knowledge of the basic concepts involved in polarization is required.

Furthermore, in optical communication systems, polarization mode dispersion has become an extremely important issue, particularly for very high-bit-rate (>10 Gb) systems. Polarization mode dispersion arises because of random birefringence present in a practical optical fiber. The birefringence that causes polarization mode dispersion in optical fibers may be linear, circular, or, in general, elliptical. In order to understand the nature of polarization mode dispersion and to control or reduce it, one must know how the various types of birefringent media affect the polarization state of the guided light while it propagates through an optical fiber. Thus, it has become almost essential for most engineers (working in the general area of photonics) to have a basic knowledge of the polarization phenomena and associated concepts, as well as the basic methods of analysis, such as Jones matrices, Stokes parameters, and the Poincaré sphere.

In this book, our aim is to provide in one source all of the basic concepts and methods involved in the understanding and design of various photonic devices, keeping the discussions as succinct as possible. The Poincaré sphere representation of polarized light is a very important method that is not discussed in sufficient detail in most of the literature. Therefore, we have devoted an entire chapter to Poincaré sphere representation, including several numerical examples to make the method very clear. This book works through all steps using many examples; therefore, even undergraduate students should be able to follow along without much difficulty.

We have been teaching various aspects of polarization to our undergraduate students and to our master's students at the Indian Institute of Technology Delhi (IITD). This book has grown out of the lecture notes that we have prepared over the last 25 years. We have also used this material in several short courses organized at IITD and at other institutions.

We thank our colleagues in the physics department of IITD for many helpful discussions - in particular, we thank Profs. B. D. Gupta, B. P. Pal, A. Sharma, M. R. Shenoy, and K. Thyagarajan, and Dr. Ravi Varshney for research collaboration and useful discussions that have helped us in improving the presentation. We are also thankful to our research students Ms. Triranjita Srivastava and Mr. Saurabh Mani Tripathi, who helped us at various stages through their suggestions, in carrying out some of the calculations, and in creating some of the diagrams. Finally, we are grateful to our wives, Shobhita and Gopa, for their patience and understanding.

We dedicate this book to the memory of our parents.

Arun Kumar

Ajoy Ghatak

New Delhi

January 2011