This book is intended as a textbook on laser physics for advanced undergraduates and first-year graduate students in physics and engineering who need to use lasers in their labs and want to understand the physical processes involved with the laser techniques in their fields of study. This book aims to provide a coherent theoretical framework on the light–matter interaction involved with lasers in such a way that students can easily understand the essential topics related to lasers and their applications and get accustomed to the latest cutting-edge research developments.