Essentials of Lasers outlines the essential principles upon which laser action depends. This book is organized into two parts encompassing 18 chapters that specifically discuss the basic theory of lasers and resonator theory. The first part deals with the principles and application of several types of lasers, including crystalline solid, gas, and semiconductor lasers. The second part describes first the features and uses of infrared and optical lasers. These topics are followed by reviews of the different components of lasers, such as amplifier and interferometer. Considerable chapters in this part contain experiments concerning the fluorescent relaxation processes and infrared emission from trivalent uranium. The remaining chapters deal with the coherent light emission from Ga As junctions and the burning hole effects in He-Ne optical laser. This book will prove useful to laser scientists, physicists, and researchers.