SOLID STATE LASER Edited by Amin H. Al-Khursan Solid State Laser Edited by Amin H. Al-Khursan Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2012 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Iva Simcic Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published February, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from [email protected] Solid State Laser, Edited by Amin H. Al-Khursan p. cm. ISBN 978-953-51-0086-7 Contents Preface IX Part 1 Waveguide Optimization in Solid-State Lasers 1 Chapter 1 Optimum Design of End-Pumped Solid-State Lasers 3 Gholamreza Shayeganrad Chapter 2 Diode Pumped Planar Waveguide/Thin Slab Solid-State Lasers 27 Jianqiu Xu Part 2 Rare-Earth Doped Lasers 61 Chapter 3 The Recent Development of Rare Earth-Doped Borate Laser Crystals 63 Chaoyang Tu and Yan Wang Chapter 4 Rare-Earth-Doped Low Phonon Energy Halide Crystals for Mid-Infrared Laser Sources 119 M. Velázquez, A. Ferrier, J.-L. Doualan and R. Moncorgé Part 3 Nonlinearity in Solid-State Lasers 143 Chapter 5 Chirped-Pulse Oscillators: Route to the Energy-Scalable Femtosecond Pulses 145 Vladimir L. Kalashnikov Chapter 6 Intra-Cavity Nonlinear Frequency Conversion with Cr3+-Colquiriite Solid-State Lasers 185 H. Maestre, A. J. Torregrosa and J. Capmany Chapter 7 Frequency Upconversion in Rare Earth Ions 209 Vineet Kumar Rai VI Contents Part 4 Semiconductor Quantum-Dot Nanostructure Lasers 225 Chapter 8 Parameters Controlling Optical Feedback of Quantum-Dot Semiconductor Lasers 227 Basim Abdullattif Ghalib, Sabri J. Al-Obaidi and Amin H. Al-Khursan Preface Even though the first laser light was emitted from a solid-state ruby crystal more than half a century ago, a wide range of applications still use solid-state lasers today. This is because they comprise a variety of materials and cover a wide range of the spectrum. Many new materials have already been discovered, but the door to add new ones is still open. Accordingly, this book covers some recent developments and reviews, to a certain extent, the work done in the past years. This book consists of eight chapters divided into four sections. The first section deals with the waveguide optimization in solid-state lasers where, in the first chapter, the optimum design of the optical coupling system and the mode matching to achieve the desired gain and thermal properties of an end-pumped laser are derived analytically. Chapter two discusses the pump uniformity, beam distortion and cooling non- uniformities in the planar waveguide guides to obtain high efficiency and good beam quality. In the second section, the rare-earth-doped lasers are discussed in chapters three and four. The recent study on the rare-earth double borate family laser crystals, in the growth, thermal, optical and spectrum characteristics are reviewed in chapter three. Then, in chapter four, the rare-earth-doped chloride and bromide laser crystals operating in bands II and III of the atmosphere transmission window are discussed. Section three (chapters five, six, and seven) deals with the nonlinearity in solid-state lasers. First, high-energy solid-state oscillators, where the levels of intensity are in the order of 1014 W/cm2, are important from a practical point of view. To exert it, the femtosecond pulse technology must be used. Such oscillators suffer from some impediment results from nonlinear effects, and when they work at the normal dispersion region, they are called “chirped pulse oscillators”. Chapter five deals with these oscillators from both theoretical, as well as experimental standpoints. In chapter six, the use of solid-state lasers in intracavity nonlinear frequency generation has been explored. However, the ability of Cr3+-doped colquiriites lasers in nonlinear conversion is discussed. A description of the physics involving second-order nonlinear interactions is presented, where the allowed processes for three-wave mixing are detailed. A review of techniques for controlling the phase matching among interacting waves is made. Another important nonlinear phenomenon is the upconversion X Preface frequency where the absorption of two or more photons is followed by the emission of a high-energy photon. The upconversion using lanthanides doped host matrices and different excitation processes, mainly the energy transfer and excitation state absorption process responsible for the luminescence in the rare earth ions, are reviewed in chapter seven. Section four deals with the nanostructure quantum dot semiconductor lasers through chapter eight, which discusses the feedback in quantum dot lasers. The delay differential equations system is used to elucidate the behavior of different states in the quantum dot laser. Finally, I wish to acknowledge the publishing process manager, Iva Simcic, for her effort and patience through the book process, and InTech for giving me this opportunity. I would also like to thank the researchers who contributed to this book. Amin H. Al-Khursan Nassiriya Nanotechnology Research Laboratory (NNRL) Physics Department, College of Science Thi-Qar University, Nassiriya Iraq Part 1 Waveguide Optimization in Solid-State Lasers 1 Optimum Design of End-Pumped Solid-State Lasers Gholamreza Shayeganrad Institute of Photonics Technologies, Department of Electrical Engineering, National Tsinghua University, Taiwan 1. Introduction The principle of laser action was first experimentally demonstrated in 1960 by T. Maiman (Maiman, 1960). This first system was a solid-state laser in which a ruby crystal and a flashlamp served as gain medium and pump source, respectively. Soon after this first laser experiment, it was realized that solid-state lasers are highly attractive sources for various scientific and industrial applications such as laser marking, material processing, holography, spectroscopy, remote sensing, lidar, optical nonlinear frequency conversion, THz frequency generation (Koechner, 2006; Hering et al., 2003; Ferguson & Zhang, 2003; Sennaroghlu, 2007). Since the early 1980’s with the development of reliable high power laser diode and the replacement of traditional flashlamp pumping by laser-diode pumping, the diode- pumped solid-state lasers, DPSSL's, have received much attention and shown the significant improvements of laser performance such as optical efficiency, output power, frequency stability, operational lifetime, linewidth, and spatial beam quality. Nd:YAG and Nd:YVO4 crystals have been extensively used as a gain medium in commercial laser products with high efficiency and good beam quality. The active ion of Nd3+ has three main transitions of 4F3/2→4I9/2, 4F3/2→4I11/2, and 4F3/2→4I13/2 with the respective emission lines of 0.94, 1.06 and 1.3 μm. The emission wavelengths of DPSSL's associated with nonlinear crystals cover a wide spectral region from ultraviolet to the mid-infrared range and very often terahertz range by difference frequency mixing process in simultaneous multi-wavelength solid-state lasers (Saha et al., 2006; Guo etal., 2010). DPSSL’s are conventionally categorized as being either end-pumped or side pumped lasers. End-pumping configuration is very popular because of higher efficiency, excellent transverse beam quality, compactness, and output stability which make it more useful for pumping tunable dye and Ti: Sapphire laser, optical parametric oscillator/amplifier, and Raman gain medium. The better beam quality is due to the high degree of spatial overlap between pump and laser modes while the high efficiency is dependent on good spatial mode-matching between the volume of pump and laser modes or nondissipating of pump energy over pumping regions that are not used by laser mode. In addition, end pumping allows the possibility of pumping a thin gain medium such as disk, slab, and microchip lasers that are not be accessed from the side-pumping (Fan &. Byer, 1998; Alfrey, 1989; Carkson & Hanna,1988; Sipes, 1985; Berger et al. 1987). 4 Solid State Laser The side-pumping geometry allows scaling to high-power operation by increasing the number of pump sources placed around the gain medium before occurring thermal fracture. In this arrangement the pump power