Content

In general, the book covers three primary areas including:

One key facet in the approach of this book is to give the reader real evidence of concepts: In the opening chapters, covering basic quantum mechanics, proof of concepts such as quantization of energy levels is provided in the form of experimental evidence - in this case the Franck-Hertz experiment. Another key facet is to provide real, useful, mathematical examples based on actual observations as opposed to ideal examples: In the fourth chapter a complete description is provided of the measurement of gain of a gas laser using an intra-cavity loss and in chapter five, experimental evidence of longitudinal modes in a laser is provided to help one of the concepts discussed in the chapter.

This book is inclusive - it contains all of the required background material (aside from basic physics such as wave optics and kinematics) required to understand laser operation. Few offerings in the field do this, and in most cases the reader is required to refer to a second or third source for background. As well, the last six chapters of the book provide a survey of the most popular and commercially-viable lasers including the helium-neon, argon and krypton ion, nitrogen, excimer, carbon-dioxide, ruby and YAG, semiconductor, and dye lasers.

This book is founded on real-world examples. Theory is presented and then applied in examples based on real laser systems. This is perhaps the strongest feature of this book and will be one very appealing to engineers and scientists in the field (who _need_ to be able to apply concepts to their particular problems) as well as to students studying laser engineering in an undergrad program who need a book showing not only the theoretical aspects of the technology but also applications.

Preface

The field of photonics is enormously broad covering everything from light sources to geometric and wave optics to fiber optics. Laser and light source technology is a subset of photonics often undersold in importance. This book focuses on these technologies with a good degree of depth without attempting be overly broad and all-inclusive of various photonics concepts. For example, fiber-optics are largely are omitted in this book except when relevant such as when fiber amplifiers are examined. Readers should find this book a refreshing mix of theory and practical example with enough mathematical detail to understand concepts and predict behavior of devices (e.g. laser gain and loss) without the use of overwhelmingly complex calculus. Where possible, a graphical approach has been taken to explain concepts such as modelocking (in chapter 7) which would otherwise require many pages of calculus to develop.

This book, targeted primarily to the scientist or engineer using this technology, promises to offer the reader a mix of theory coupled with practical, real-world examples based on real laser systems. This book will begin with a look at the basics of light emission including blackbody radiation and atomic emission followed by an outline of quantum mechanics. For some readers this will be a basic review however the availability of the background material alleviates the necessity to constantly refer back to a second (or third) book on that subject. Throughout the book practical, solved, examples are embedded within each chapter and are founded on real-world laser systems allowing the direct application of concepts covered. Case studies in the later chapters allows the reader to further apply concepts in the text to real-world laser systems.

This book is also ideal for students in an undergraduate course on lasers and light sources. Indeed, the original design of this book was for a textbook for an applied degree course (actually, two courses) in laser engineering. Unlike many existing texts which cover this material in a single chapter this particular book has depth allowing the reader to delve into the intricacies. Chapter problems assist the reader by challenging him or her to further make the jump between theory and reality. This book will serve well as a text for a single course in laser technology or two courses where a laboratory component is present. Introductory chapters on blackbody radiation, atomic emission, and quantum mechanics allow this text to be used without the requirement of a second or third textbook to cover these topics which are often omitted in similar texts. It is assumed that students will already have a grasp on geometric and wave optics (including the concepts of interference and diffraction) as well as basic first-year physics including kinematics.

This text begins (in chapter 1) with a look at the most basic source of light of all, blackbody radiation, and includes a look at standard applications (such as incandescent lighting) as well as newer applications such as far-IR viewers capable of 'seeing' a human body hidden in truck! Chapter 2 is a look at atomic emission in which we examine the nature and origins of emission of light from electrically excited gases as well as mechanisms such as fluorescence with applications ranging from common fluorescent lamps to vacuum-fluorescent displays and colored neon tubes. The chapter concludes with a look at semiconductor light sources (LEDs). As well as theory on atomic emission (such as the origins of line spectra) this chapter also includes practical details of spectroscopy including operating principles of a spectroscope and examples of usage in identifying unknown gas samples which serve to reinforce the usefulness of the entire theory of atomic structure with practical applications.

Investigation of both blackbody radiation as well as atomic emission light leads us on a pathway to quantum mechanics (in chapter 3), vital to understanding the mechanisms responsible for light emission at an atomic level and later for understanding the origins of transitions responsible for laser emission in the ultraviolet, visible, and infrared regions of the spectrum. While few books include this topic, it is vital to understanding emission spectra as well as basic laser processes and so is included in the book for some readers as a review, for others as a new topic.

In chapter 4 we begin with a fundamental look at lasers and lasing action. Aside from the basic processes such as stimulated emission and rate equations governing lasing action this chapter also outlines key laser mechanisms such as pumping, the requirement for feedback (examined in detail in chapter 6), and gain and loss in a real laser. Real-world examples are embedded within the chapter such as noise in a fiber amplifier (ASE) which demonstrates the rate equations in action as well as details of an experiment in which the gain of a gas laser is measured by insertion of a variable loss into the optical cavity. Chapter 5 examines lasing transitions in detail including selective pumping mechanisms and laser energy level systems (three and four level lasers). Examples of transitions and energies in real laser systems are given along side theoretical examples allowing the reader to compare how well theoretical models fit real laser systems.

As well as an expansion on the concepts of gain and loss introduced in chapter 4, chapter 6 examines the laser resonator as an interferometer. The mathematical requirements for stability of resonator and longitudinal and transverse modes in a real resonator are detailed. Wavelength selection mechanisms including gratings, prisms, and etalons are outlined in this chapter with examples of applications in practical lasers such as single frequency tuning of a line in an argon laser.

Chapter 7 provides the reader with an introduction to techniques used to produce fast pulses such as Q-switching and modelocking. In the case of modelocking a graphical approach is used to illustrate how the pulse is formed from many simultaneous longitudinal modes. Finally chapter 8 covers non-linear optics as they apply to lasers. Harmonic generation and optical parametric oscillators (OPOs) are examined.

The last six chapters of this book provide case studies allowing the reader to see the practical application of laser theory. The lasers chosen represent the vast majority of commercially-available lasers allowing the reader to relate the theory learned to practical lasers he/she encounters in the laboratory or the manufacturing environment. In these chapters various lasers will be outlined with respect to the lasing process involved (including quantum mechanics, energy levels, and transitions), details of the laser itself (lasing medium, cooling requirements), power sources for the laser, applications, and a survey of commercially-available lasers of that type. Visible gas lasers, including helium-neon and ion lasers, are covered in chapter 9. UV gas lasers such as nitrogen and excimer lasers are covered in chapter 10 including details of the unique constraints on electrical pumping for these types of lasers. Chapter 11 examines infrared gas lasers focussing primarily on the carbon-dioxide and similar lasers using rotational and vibrational transitions.

Chapter 12 details common solid-state lasers including YAG and ruby. Pump sources including flashlamps, CW arc lamps, and semiconductor lasers will be examined as well as techniques such as non-linear harmonic generation (often used with these lasers). Chapter 13 details the basics of semiconductor lasers, and finally chapter 14 covers dye lasers which feature wide continuously-tunable wavelength ranges and are often used in modelocking schemes to generate extremely short pulses of laser radiation. In each of these case study chapters, photographs and details have been included allowing the reader to see the structure of each laser. Chapter 10, for example, includes numerous photographs of the various structures in a real excimer laser including details of the electrodes and preionizers, the cooling system and heat exchanger, as well as electrical components such as the energy storage capacitor and thyratron trigger. In each case a clear explanation is given guiding the reader to understanding the function of each critical component.