The first laser was fabricated in 1960, and since then there has been a renaissance in the field of optics. From laser physics to optical amplifiers, fiber optics to optical communications, optical design to holography, ultra-short pulse generation to non-linear phenomena, optics now finds important applications in almost all branches of science and engineering. Because of this, an undergraduate course in optics has become a “must” not only for students of physics but of engineering as well. Although it is impossible to cover all areas in one single book, this book attempts to give a comprehensive account of a large number of important topics in this exciting field. It should meet the requirements of a course on optics meant for undergraduate students of science and engineering.

The first edition of this book appeared in 1977 and it is indeed a matter of great satisfaction that during the past 27 years, the book has been received well by the academic community in India. I have used this book several times in teaching the undergraduate course on optics to engineering students as well as to students of engineering physics at IIT Delhi, and have felt the necessity of rewriting certain portions of the book.

Revision Work in this Edition Several chapters from the previous edition have been completely rewritten and a large number of topics have been newly introduced. In addition,

• All figures have been redrawn. A large number of figures now correspond to actual numerical calculations which have been generated using softwares like GNUPLOT and Mathematica. Many new diagrams have been added for easier understanding of difficult concepts—some of these diagrams give a three dimensional perspective of the phenomenon.

• Every chapter now starts with important milestones in the area. This would give a historical perspective of the topic.

• Each chapter now ends with a summary of important results derived in the chapter. This is a new feature and should be of value to students.

• Numerous worked out examples have been added so that the book can also be used for self study.

• Most quotations that appear at various part of the text are now of famous physicists rather than those of poets and authors and they reflect the importance of the subject.

Organisation of the Book As in the first edition of the book, the present edition also attempts to give a balanced account of traditional optics as well as some of the recent developments in this field. The plan of the present edition is as follows:

• The first chapter gives important milestones in optics and a historical introduction to the subject discussing the nature of light.

• The following four chapters are on geometrical optics including ray tracing through graded-index media explaining in detail the phenomena of mirage and looming and also reflection from the ionosphere. The matrix method in paraxial optics, which is extensively used in the industry, has been discussed in detail in a separate chapter.

• The next five chapters discuss the origin of refractive index and the basic physics of wave propagation including Huygens’ principle. Many interesting experiments (like the redness of the setting sun, water waves, shock waves, etc.) are discussed. The concepts of group velocity and pulse dispersion have been discussed in great detail.

• Chapters 11 to 14 cover the very important and interesting area of interference and many beautiful experiments associated with it—the underlying principle is the superposition principle which is discussed in detail in Chapter 11. In Chapter 13, the Michelson Interferometer is discussed which is perhaps one of the most ingenious and sensational optical instrument for which Michelson received the Nobel Prize in Physics in 1907. Chapter 14 discusses the Fabry – Perot interferometer which is based on multiple beam interference and is characterized by a high resolving power and hence finds applications in high resolution spectroscopy.

• Chapter 15 discusses the basic concept of temporal and spatial coherence. The ingenious experiment of Michelson, which used the concept of spatial coherence to determine the angular diameter of stars, has been discussed in detail. Topics like optical beats and Fourier transform spectroscopy have also been discussed.

• Chapters 16 and 17 cover the very important area of diffraction and discuss the principle behind topics like diffraction divergence of laser beams, resolving power of telescopes, laser focusing, spatial frequency filtering, X-ray diffraction etc.

• Chapter 18 is on holography, giving the underlying principle and many applications. Dennis Gabor received the 1971 Nobel Prize in Physics for discovering the principle of holography.

• Chapters 19 and 20 are on the electromagnetic character of waves and the first chapter discusses propagation of electromagnetic waves in anisotropic media in great detail including first principle derivations of wave and ray velocities. Also applications like optical activity, Faraday rotation etc. have been discussed. Reflection and refraction of electromagnetic waves by a dielectric interface has been discussed in Chapter 21. The results directly explain phenomena like Brewster’s law, total internal reflection, evanescent waves, Fabry–Perot transmission resonances, etc.

• Chapter 22 is on the particle model of radiation—for which Einstein received the 1921 Nobel Prize. The chapter also discusses the Compton effect (for which Professor Compton received the 1927 Nobel Prize in Physics) which established that the photon has a momentum equal to h/l.

• Chapter 23 is on lasers—a subject of tremendous technological importance. The basic physics of lasers along with their special characteristics are also discussed. Townes, Prochorov and Basov shared the 1964 Nobel Prize in Physics for developing lasers.

• Chapter 24 is on fiber optics—an area that has revolutionized communication. The chapter discusses the basic principles of the optical fiber with applications in fiber optic communication systems; the chapter also gives a very brief account of fiber-optic sensors.

In summary, the book discusses topics that have made tremendous impact in the growth of science and technology. Although the chapter titles remain almost the same as in the second edition, Chapters 2, 6, 7, 8, 13, 14, 16, 17, 19, 20, 23 and 24 have been completely rewritten and expanded. Many new examples (with illustrative diagrams) have been drawn to clarify important concepts and point out important applications. For example, Chapter 2 has been completely rewritten to give many new examples of graded index optics including the reflection of radio waves by the atmosphere. Chapter 8 is entirely new and discusses the very important concept of pulse dispersion and chirping. In Chapters 12 and 13, many sections have been rewritten, many new figures have been added and a new section on Fiber Bragg Gratings has been introduced. Chapter 14, on Multiple Beam Interferometry has been completely rewritten and many new examples have been added. Chapters 17, 18, 19, 22, 23 and 24 have also been completely rewritten and many new examples have been added.

The book should ideally meet the requirements of undergraduate students of science and engineering and should stimulate the students for further studies in this exciting area. Researchers in academic institutes and industries involved in optical communication and in the fabrication and application of lasers should find the book very useful.

The first edition of the book was dedicated to my research students: my continuous interactions with them have led to a deeper understanding of optics; I end with the quotation (which I found in a book by G.L. Squires): “I have learnt much from my teachers, but more from my pupils. To all my pupils, I owe a very special debt.”

I will be very grateful for suggestions for further improvement of the book. My email address is ajoykghatak@yahoo.com.

Acknowledgements My sincere thanks to Professor I.C. Goyal who constantly encouraged me to rewrite certain portions of the book and bring out a new edition. He had also pointed out several typographical errors in the second edition. I am also grateful to Professor M. S. Sodha who had encouraged me to write the first edition and who always supported me in my endeavors. My grateful thanks to Professor Thyagarajan for allowing me to use some of his unpublished notes. I thank again Dr. G. Bose, Professor Lalit Malhotra, Professor Bishnu Pal, Professor Anurag Sharma, Professor R. S. Sirohi, Professor K. Thyagarajan and Professor C. S. Vikram for their help in writing some portions of the earlier editions of the book (which also appear in the present edition) and providing me some photographs for the book. I would also like to thank my other colleagues Dr. B. D. Gupta, Professor Ajit Kumar, Professor Arun Kumar, Dr. M.R. Shenoy, Professor Kehar Singh and Dr. Ravi Varshney for numerous stimulating discussions. I would also like to thank Professor GI Opat of University of Melbourne for his kind invitation to attend the 1989 conference on Teaching of Optics which gave me many ideas as to how to make difficult concepts in optics easy to understand. I also thank Mr. Monish Das and Mr. Debasish Roy for their help in the preparation of the manuscript. Finally, I owe a lot to my family—particularly to my wife Gopa—for allowing me to spend long hours in preparing this difficult manuscript and for her support all along.

Ajoy Ghatak