There is hardly any book that aims at solving problems typically encountered in the laser field, and this book intends to fill the void. Following some initial exercises related to general aspects in laser physics (Chapt. 1), the subsequent problems are organized along the following topics: (i) Interaction of radiation with matter either made of atoms or ions, weakly interacting with surrounding species, or made of more complicated elements such as molecules or semiconductors (Chapters 2 and 3). (ii) Wave propagation in optical media and optical resonators (Chapters 4 and 5). (iii) Optical and electrical pumping processes and systems (Chapter 6): (iv) Continuous wave and transient laser behaviors (Chapters 7 and 8). (v) Solid-state, dye, semiconductor, gas and X-ray lasers (Chapters 9 and 10). (vi) Proper­ ties of the output beam and beam transformation by amplification, frequency conversion and pulse compression or expansion (Chapters 11 and 12). Problems are proposed here and solved following the contents of Orazio Svelto's Principles of Lasers (fourth edition; Plenum Press, New York, 1998). Whenever needed, equations and figures of the book mentioned above are currently used with an appropriate reference [e. g. , Eq. (1. Ll) of the book is referred to as Eq. (Ll. 1) of PL]. One can observe, however, that the types of problems proposed and discussed are of general validity and many of these problems have actually been suggested by our own long-time experience in performing theoretical and experimental researches in the field.

This book is motivated by the very favorable reception given to the previous editions as well as by the considerable range of new developments in the laser ?eld since the publication of the third edition in 1989. These new developmentsinclude, among others, Quantum-Well and Multiple-Quantum Well lasers, diode-pumpedsolid-state lasers, new concepts for both stable and unstable resonators, femtosecond lasers, ultra-high-brightness lasers etc. The basic aim of the book has remained the same, namely to providea broad and uni?ed description of laser behavior at the simplest level which is compatible with a correct physical understanding. The book is thereforeintendedas a text-bookfor a senior-levelor ?rst-year graduatecourse and/or as a reference book. This edition corrects several errors introduced in the previous edition. The most relevant additions or changes to since the third edition can be summarized as follows: 1. A much-more detailed description of Ampli?ed Spontaneous Emission has been given [Chapt. 2] and a novel simpli?ed treatment of this phenomenon both for homogeneousor inhomogeneouslines has been introduced [Appendix C]. 2. A major fraction of a chapter [Chapt.3] is dedicated to the interaction of radiation with semiconductor media, either in a bulk form or in a quantum-con?ned structure (quantum-well, quantum-wire and quantum dot). 3. A moderntheory of stable and unstable resonatorsis introduced,where a more ext- sive use is made of the ABCD matrix formalism and where the most recent topics of dynamically stable resonators as well as unstable resonators, with mirrors having Gaussian or super-Gaussian transverse re?ectivity pro?les, are considered [Chapt. 5].

This volume is a collection of papers presented at the Ninth International Symposium on "Ultrafast Processes in Spectroscopy" (UPS '95) held at the International Centre for Theo­ retical Physics (ICTP), Trieste (Italy), October 30 -November 3, 1995. These meetings have become recognized as the major forum in Europe for discussion of new work in this rapidly moving field. The UPS'95 Conference in Trieste brought together a multidisciplinary group of researchers sharing common interests in the generation of ultrashort optical pulses and their application to studies of ultrafast phenomena in physics, chemistry, material science, electronics, and biology. It was attended by approximately 250 participants from 20 countries and the five-day program comprises more than 200 papers. The progress of both technology and applications in the field of ultrafast processes during these last years is truly remarkable. The advent of all solid state femtosecond lasers and the extension of laser wavelengths by frequency conversion techniques provide a large variety of high-performance light sources for ultrashort pulses. With these sources ultrafast phenomena in physical, chemical and biological systems and in electronic de­ vi(:es are now studied extensively. Ultrafast technology is becoming one of the basic and common tools presently entering a wide variety of scientific fields not only for basic re­ search but also for promoting new applications in various areas. We feel that these pro­ ceedings vividly reflect the present status of the field.

There is hardly any book that aims at solving problems typically encountered in the laser field, and this book intends to fill the void. Following some initial exercises related to general aspects in laser physics (Chapt. 1), the subsequent problems are organized along the following topics: (i) Interaction of radiation with matter either made of atoms or ions, weakly interacting with surrounding species, or made of more complicated elements such as molecules or semiconductors (Chapters 2 and 3). (ii) Wave propagation in optical media and optical resonators (Chapters 4 and 5). (iii) Optical and electrical pumping processes and systems (Chapter 6): (iv) Continuous wave and transient laser behaviors (Chapters 7 and 8). (v) Solid-state, dye, semiconductor, gas and X-ray lasers (Chapters 9 and 10). (vi) Proper­ ties of the output beam and beam transformation by amplification, frequency conversion and pulse compression or expansion (Chapters 11 and 12). Problems are proposed here and solved following the contents of Orazio Svelto''s Principles of Lasers (fourth edition; Plenum Press, New York, 1998). Whenever needed, equations and figures of the book mentioned above are currently used with an appropriate reference [e. g. , Eq. (1. Ll) of the book is referred to as Eq. (Ll. 1) of PL]. One can observe, however, that the types of problems proposed and discussed are of general validity and many of these problems have actually been suggested by our own long-time experience in performing theoretical and experimental researches in the field.

This volume is a collection of papers presented at the Ninth International Symposium on "Ultrafast Processes in Spectroscopy" (UPS ''95) held at the International Centre for Theo­ retical Physics (ICTP), Trieste (Italy), October 30 -November 3, 1995. These meetings have become recognized as the major forum in Europe for discussion of new work in this rapidly moving field. The UPS''95 Conference in Trieste brought together a multidisciplinary group of researchers sharing common interests in the generation of ultrashort optical pulses and their application to studies of ultrafast phenomena in physics, chemistry, material science, electronics, and biology. It was attended by approximately 250 participants from 20 countries and the five-day program comprises more than 200 papers. The progress of both technology and applications in the field of ultrafast processes during these last years is truly remarkable. The advent of all solid state femtosecond lasers and the extension of laser wavelengths by frequency conversion techniques provide a large variety of high-performance light sources for ultrashort pulses. With these sources ultrafast phenomena in physical, chemical and biological systems and in electronic de­ vi(:es are now studied extensively. Ultrafast technology is becoming one of the basic and common tools presently entering a wide variety of scientific fields not only for basic re­ search but also for promoting new applications in various areas. We feel that these pro­ ceedings vividly reflect the present status of the field.

This second edition, appearing about twenty years after the discovery of the laser is a substantially revised version of the first edition. It is, like the first, aimed at both classroom teaching and self-study by technical personnel interested in learning the principles of laser operation. In preparing the second edition the hope has been that both these aims will be better served as a result of the various improvements made. The main changes have been made with the following aims in mind: (i) To update the book. Thus new topics have been added (in particular on various new types of lasers, e. g. , rare-gas-halide excimer lasers, color-center lasers, and free-electron lasers), while on the other hand some topics have been given less emphasis (again this applies particularly to some types of lasers, e. g. , the ruby laser). Updating is especially important in the area of laser applications, and the chapter on this topic has therefore been com­ pletely rewritten. (ii) To make some improvements to the logical consis­ tency of the book by rearranging material and adding new material. Thus a few topics have been moved from one section to another and a new chapter entitled Laser Beam Transformation has been added. (iii) To further reduce the mathematical content, placing greater emphasis on physical descrip­ tions of phenomena.

This third edition, motivated by the numerous and significant developments in the laser field since the publication of the second edition in 1982, is a substantially revised version of the previous edition. The basic philosophy has, however, remained the same, namely, to provide a broad and unified descrip­ tion of laser behavior at the simplest level that is compatible with a correct physical understanding. The basic organization of the book has also remained the same. The book is therefore aimed at both classroom teaching and self-study by students in electrical engineering, physics, and chemistry who have an interest in understanding the principles of laser operation. The major additions to this edition are the following: 1. New sections dealing with laser types, in particular x-ray lasers and new solid-state lasers, including alexandrite devices, and a greatly extended description of semiconductor lasers. 2. A more extended treatment of laser mode-locking, including new sections on cavity dumping and pulse compression. 3. A more extended and greatly simplified description of the coherence and statistical properties of laser light as opposed to those of conven­ tional light. 4. A greatly extended discussion of the physics of gas discharges. Other important additions include a discussion of some topics from conven­ tional optics (e.g., ray matrix methods, Fabry-Perot interferometers, and multilayer dielectric mirrors), Gaussian beam propagation (e.g., the ABeD law), and the theory of relaxation oscillations and active mode-locking.

This book is motivated by the very favorable reception given to the previous editions as well as by the considerable range of new developments in the laser field since the publication of the third edition in 1989. These new developments include, among others, quantum-well and muitiple-quantum-welliasers, diode-pumped solid-state lasers, new concepts for both stable and unstable resonators, femtosecond lasers, ultra-high-brightness lasers, etc. This edition thus represents a radically revised version of the preceding edition, amounting essentially to a new book in its own right. However, the basic aim has remained the same, namely to provide a broad and unified description of laser behavior at the simplest level which is compatible with a correct physical understanding. The book is therefore intended as a textbook for a senior-level or first-year graduate course and/or as a reference book. The most relevant additions or changes to this edition can be summarized as follows: 1. A much-more detailed description of Amplified Spontaneous Emission has been given (Chapter 2) and a novel simplified treatment of this phenomenon, both for homogeneous and inhomogeneous lines, has been introduced (Appendix C). 2. A major fraction of a new chapter (Chapter 3) is dedicated to the interaction of radiation with semiconductor media, either in a bulk form or in a quantum-confined structure (quantum-well, quantum-wire and quantum dot). 3.

This book is the result of more than ten years of research and teaching in the field of quantum electronics. The purpose of the book is to introduce the principles of lasers, starting from elementary notions of quantum mechanics and electromagnetism. Because it is an introductory book, an effort has been made to make it self­ contained to minimize the need for reference to other works. For the same reason; the references have been limited (whenever possible) either to review papers or to papers of seminal importance. The organization of the book is based on the fact that a laser can be thought of as consisting of three elements: (i) an active material, (ii) a pumping system, and (iii) a suitable resonator. Ac­ cordingly, after an introductory chapter, the next three chapters deal, respectively, with the interaction of radiation with matter, pumping processes, and the theory of passive optical resonators.

There is hardly any book that aims at solving problems typically encountered in the laser field, and this book intends to fill the void. Following some initial exercises related to general aspects in laser physics (Chapt. 1), the subsequent problems are organized along the following topics: (i) Interaction of radiation with matter either made of atoms or ions, weakly interacting with surrounding species, or made of more complicated elements such as molecules or semiconductors (Chapters 2 and 3). (ii) Wave propagation in optical media and optical resonators (Chapters 4 and 5). (iii) Optical and electrical pumping processes and systems (Chapter 6): (iv) Continuous wave and transient laser behaviors (Chapters 7 and 8). (v) Solid-state, dye, semiconductor, gas and X-ray lasers (Chapters 9 and 10). (vi) Proper­ ties of the output beam and beam transformation by amplification, frequency conversion and pulse compression or expansion (Chapters 11 and 12). Problems are proposed here and solved following the contents of Orazio Svelto's Principles of Lasers (fourth edition; Plenum Press, New York, 1998). Whenever needed, equations and figures of the book mentioned above are currently used with an appropriate reference [e. g. , Eq. (1. Ll) of the book is referred to as Eq. (Ll. 1) of PL]. One can observe, however, that the types of problems proposed and discussed are of general validity and many of these problems have actually been suggested by our own long-time experience in performing theoretical and experimental researches in the field.

This book is motivated by the very favorable reception given to the previous editions as well as by the considerable range of new developments in the laser ?eld since the publication of the third edition in 1989. These new developmentsinclude, among others, Quantum-Well and Multiple-Quantum Well lasers, diode-pumpedsolid-state lasers, new concepts for both stable and unstable resonators, femtosecond lasers, ultra-high-brightness lasers etc. The basic aim of the book has remained the same, namely to providea broad and uni?ed description of laser behavior at the simplest level which is compatible with a correct physical understanding. The book is thereforeintendedas a text-bookfor a senior-levelor ?rst-year graduatecourse and/or as a reference book. This edition corrects several errors introduced in the previous edition. The most relevant additions or changes to since the third edition can be summarized as follows: 1. A much-more detailed description of Ampli?ed Spontaneous Emission has been given [Chapt. 2] and a novel simpli?ed treatment of this phenomenon both for homogeneousor inhomogeneouslines has been introduced [Appendix C]. 2. A major fraction of a chapter [Chapt.3] is dedicated to the interaction of radiation with semiconductor media, either in a bulk form or in a quantum-con?ned structure (quantum-well, quantum-wire and quantum dot). 3. A moderntheory of stable and unstable resonatorsis introduced,where a more ext- sive use is made of the ABCD matrix formalism and where the most recent topics of dynamically stable resonators as well as unstable resonators, with mirrors having Gaussian or super-Gaussian transverse re?ectivity pro?les, are considered [Chapt. 5].

This volume is a collection of papers presented at the Ninth International Symposium on "Ultrafast Processes in Spectroscopy" (UPS '95) held at the International Centre for Theo­ retical Physics (ICTP), Trieste (Italy), October 30 -November 3, 1995. These meetings have become recognized as the major forum in Europe for discussion of new work in this rapidly moving field. The UPS'95 Conference in Trieste brought together a multidisciplinary group of researchers sharing common interests in the generation of ultrashort optical pulses and their application to studies of ultrafast phenomena in physics, chemistry, material science, electronics, and biology. It was attended by approximately 250 participants from 20 countries and the five-day program comprises more than 200 papers. The progress of both technology and applications in the field of ultrafast processes during these last years is truly remarkable. The advent of all solid state femtosecond lasers and the extension of laser wavelengths by frequency conversion techniques provide a large variety of high-performance light sources for ultrashort pulses. With these sources ultrafast phenomena in physical, chemical and biological systems and in electronic de­ vi(:es are now studied extensively. Ultrafast technology is becoming one of the basic and common tools presently entering a wide variety of scientific fields not only for basic re­ search but also for promoting new applications in various areas. We feel that these pro­ ceedings vividly reflect the present status of the field.

There is hardly any book that aims at solving problems typically encountered in the laser field, and this book intends to fill the void. Following some initial exercises related to general aspects in laser physics (Chapt. 1), the subsequent problems are organized along the following topics: (i) Interaction of radiation with matter either made of atoms or ions, weakly interacting with surrounding species, or made of more complicated elements such as molecules or semiconductors (Chapters 2 and 3). (ii) Wave propagation in optical media and optical resonators (Chapters 4 and 5). (iii) Optical and electrical pumping processes and systems (Chapter 6): (iv) Continuous wave and transient laser behaviors (Chapters 7 and 8). (v) Solid-state, dye, semiconductor, gas and X-ray lasers (Chapters 9 and 10). (vi) Proper­ ties of the output beam and beam transformation by amplification, frequency conversion and pulse compression or expansion (Chapters 11 and 12). Problems are proposed here and solved following the contents of Orazio Svelto''s Principles of Lasers (fourth edition; Plenum Press, New York, 1998). Whenever needed, equations and figures of the book mentioned above are currently used with an appropriate reference [e. g. , Eq. (1. Ll) of the book is referred to as Eq. (Ll. 1) of PL]. One can observe, however, that the types of problems proposed and discussed are of general validity and many of these problems have actually been suggested by our own long-time experience in performing theoretical and experimental researches in the field.

This volume is a collection of papers presented at the Ninth International Symposium on "Ultrafast Processes in Spectroscopy" (UPS ''95) held at the International Centre for Theo­ retical Physics (ICTP), Trieste (Italy), October 30 -November 3, 1995. These meetings have become recognized as the major forum in Europe for discussion of new work in this rapidly moving field. The UPS''95 Conference in Trieste brought together a multidisciplinary group of researchers sharing common interests in the generation of ultrashort optical pulses and their application to studies of ultrafast phenomena in physics, chemistry, material science, electronics, and biology. It was attended by approximately 250 participants from 20 countries and the five-day program comprises more than 200 papers. The progress of both technology and applications in the field of ultrafast processes during these last years is truly remarkable. The advent of all solid state femtosecond lasers and the extension of laser wavelengths by frequency conversion techniques provide a large variety of high-performance light sources for ultrashort pulses. With these sources ultrafast phenomena in physical, chemical and biological systems and in electronic de­ vi(:es are now studied extensively. Ultrafast technology is becoming one of the basic and common tools presently entering a wide variety of scientific fields not only for basic re­ search but also for promoting new applications in various areas. We feel that these pro­ ceedings vividly reflect the present status of the field.

This second edition, appearing about twenty years after the discovery of the laser is a substantially revised version of the first edition. It is, like the first, aimed at both classroom teaching and self-study by technical personnel interested in learning the principles of laser operation. In preparing the second edition the hope has been that both these aims will be better served as a result of the various improvements made. The main changes have been made with the following aims in mind: (i) To update the book. Thus new topics have been added (in particular on various new types of lasers, e. g. , rare-gas-halide excimer lasers, color-center lasers, and free-electron lasers), while on the other hand some topics have been given less emphasis (again this applies particularly to some types of lasers, e. g. , the ruby laser). Updating is especially important in the area of laser applications, and the chapter on this topic has therefore been com­ pletely rewritten. (ii) To make some improvements to the logical consis­ tency of the book by rearranging material and adding new material. Thus a few topics have been moved from one section to another and a new chapter entitled Laser Beam Transformation has been added. (iii) To further reduce the mathematical content, placing greater emphasis on physical descrip­ tions of phenomena.

This third edition, motivated by the numerous and significant developments in the laser field since the publication of the second edition in 1982, is a substantially revised version of the previous edition. The basic philosophy has, however, remained the same, namely, to provide a broad and unified descrip­ tion of laser behavior at the simplest level that is compatible with a correct physical understanding. The basic organization of the book has also remained the same. The book is therefore aimed at both classroom teaching and self-study by students in electrical engineering, physics, and chemistry who have an interest in understanding the principles of laser operation. The major additions to this edition are the following: 1. New sections dealing with laser types, in particular x-ray lasers and new solid-state lasers, including alexandrite devices, and a greatly extended description of semiconductor lasers. 2. A more extended treatment of laser mode-locking, including new sections on cavity dumping and pulse compression. 3. A more extended and greatly simplified description of the coherence and statistical properties of laser light as opposed to those of conven­ tional light. 4. A greatly extended discussion of the physics of gas discharges. Other important additions include a discussion of some topics from conven­ tional optics (e.g., ray matrix methods, Fabry-Perot interferometers, and multilayer dielectric mirrors), Gaussian beam propagation (e.g., the ABeD law), and the theory of relaxation oscillations and active mode-locking.

This book is motivated by the very favorable reception given to the previous editions as well as by the considerable range of new developments in the laser field since the publication of the third edition in 1989. These new developments include, among others, quantum-well and muitiple-quantum-welliasers, diode-pumped solid-state lasers, new concepts for both stable and unstable resonators, femtosecond lasers, ultra-high-brightness lasers, etc. This edition thus represents a radically revised version of the preceding edition, amounting essentially to a new book in its own right. However, the basic aim has remained the same, namely to provide a broad and unified description of laser behavior at the simplest level which is compatible with a correct physical understanding. The book is therefore intended as a textbook for a senior-level or first-year graduate course and/or as a reference book. The most relevant additions or changes to this edition can be summarized as follows: 1. A much-more detailed description of Amplified Spontaneous Emission has been given (Chapter 2) and a novel simplified treatment of this phenomenon, both for homogeneous and inhomogeneous lines, has been introduced (Appendix C). 2. A major fraction of a new chapter (Chapter 3) is dedicated to the interaction of radiation with semiconductor media, either in a bulk form or in a quantum-confined structure (quantum-well, quantum-wire and quantum dot). 3.

This book is the result of more than ten years of research and teaching in the field of quantum electronics. The purpose of the book is to introduce the principles of lasers, starting from elementary notions of quantum mechanics and electromagnetism. Because it is an introductory book, an effort has been made to make it self­ contained to minimize the need for reference to other works. For the same reason; the references have been limited (whenever possible) either to review papers or to papers of seminal importance. The organization of the book is based on the fact that a laser can be thought of as consisting of three elements: (i) an active material, (ii) a pumping system, and (iii) a suitable resonator. Ac­ cordingly, after an introductory chapter, the next three chapters deal, respectively, with the interaction of radiation with matter, pumping processes, and the theory of passive optical resonators.