ndustrial laser systems for material processing applications rely on the availability of highly efficient, high-brightness diode lasers. GaAs-based broad-area laser bars play a vital role in such applications as pump sources for high-beam-quality solid-state lasers and, increasingly, as direct processing tools. This work studies 940 nm-laser bars emitting 1 kW optical power at room temperature, identifying those physical mechanisms that are currently limiting electrical-to-optical conversion efficiency as well as lateral beam quality. In the process, several diagnostic studies on bars with varied lateral-longitudinal design were carried out. The effects of technological measures for performance optimization were analyzed, yielding a new benchmark in efficiency and lateral divergence. The studies into altered resonator lengths of 4 and 6 mm as well as fill factors between 69 and 87 % successfully reduce both the voltage dropping across the device and power saturation at high currents, enabling 66 % efficiency at the operation point. Concrete measures how to reach efficiencies ≥70 % are presented thereafter, showing that doubling the efficiency value of the first 1 kW-demonstration in 2007 – amounting to 35 % – is in near reach. Investigation of the beam quality bases on a herein proposed and realized concept, in which the far field is resolved for each individual bar emitter. In this way, it is possible to determine how far-field profiles vary along the bar width and how much these variations affect the overall bar far-field. Further, such effects specific to bar structures can be separated into non-thermal and thermal influences. The effect of mechanical chip deformation (bar smile) as well as neighboring-emitter interaction has been investigated for the first time in active kW-class devices, yielding a lateral divergence as low as 8.8° at the operation point.

Edge-emitting quantum-well diode lasers based on GaAs combine a high conversion efficiency, a wide range of emission wavelengths covering a span from 630 nm to 1180 nm, and the ability to achieve high output powers. The often used longitudinal-invariant Fabry-Pérot-type resonators are easy to design but often lead to functionality or performance limitations. In this work, the application of laterally-longitudinally non-uniform resonator configurations is explored as a way to reduce unwanted and performance-limiting effects. The investigations are carried out on existing and entirely newly developed laser designs using dedicated simulation tools. These include a sophisticated time-dependent laser simulator based on a traveling-wave model of the optical fields in the lateral-longitudinal plane and a Maxwell solver based on the eigenmode expansion method for the simulation of passive waveguides. Whenever possible, the simulation results are compared with experimental data. Based on this approach, three fundamentally different laser types are investigated: • Dual-wavelength lasers emitting two slightly detuned wavelengths around 784 nm out of a single aperture • Ridge-waveguide lasers with tapered waveguide and contact layouts that emit light of a wavelength of around 970 nm • Broad-area lasers with slightly tapered contact layouts emitting at 910 nm The results of this thesis underline the potential of lateral-longitudinal non-uniform laser designs to increase selected aspects of device performance, including beam quality, spectral stability, and output power.

During the past years, wireless communication systems have been rapidly advancing to meet the high data-rate requirements of various emerging applications. However, the existing transceivers have typically been demonstrated using CMOS-compatible technologies that deliver a relatively low equivalent isotropic radiated power in a small unit cell. Moreover, the particular device characteristics are limiting the linear region for operation. Therefore, the main focus of this dissertation is to present and discuss new design methods for transceivers to solve these issues. To reduce the complexity of the transceiver module for further phased-array scaling, a low-noise power amplifier design approach is designed using a 0.15-μm GaN-on-SiC high-electron mobility transistor technology (HEMT). Utilizing a traded off interstage matching topology between loss and bandwidth, the conversion loss induced by the matching network could be effectively reduced. A stacked-FET configuration was adopted to enhance the power handling of the RF switch. Further improvement on the isolation bandwidth was investigated using theoretical analysis on the intrinsic effect of the passive HEMTs. With the successful implementation of the RF front-end circuits, transceiver modules were integrated on Rogers RO3010 substrate. The planar dual exponentially tapered slot antenna phased-array system showed a compact size with simple biasing network compared to the conventional transceiver approach. The presented T/R module was characterized with an over-the-air test at a distance of 1 m, overcoming the free space path loss of 64 dB. It also shows a high flexibility for further integration with a larger number of array systems, which is very promising for future 5G communication systems.

Semiconductor lasers have important applications in numerous fields, including engineering, biology, chemistry and medicine. They form the backbone of the optical telecommunications infrastructure supporting the internet, and are used in information storage devices, bar-code scanners, laser printers and many other everyday products. Semiconductor lasers: Fundamentals and applications is a comprehensive review of this vital technology.Part one introduces the fundamentals of semiconductor lasers, beginning with key principles before going on to discuss photonic crystal lasers, high power semiconductor lasers and laser beams, and the use of semiconductor lasers in ultrafast pulse generation. Part two then reviews applications of visible and near-infrared emitting lasers. Nonpolar and semipolar GaN-based lasers, advanced self-assembled InAs quantum dot lasers and vertical cavity surface emitting lasers are all considered, in addition to semiconductor disk and hybrid silicon lasers. Finally, applications of mid- and far-infrared emitting lasers are the focus of part three. Topics covered include GaSb-based type I quantum well diode lasers, interband cascade and terahertz quantum cascade lasers, whispering gallery mode lasers and tunable mid-infrared laser absorption spectroscopy.With its distinguished editors and international team of expert contributors, Semiconductor lasers is a valuable guide for all those involved in the design, operation and application of these important lasers, including laser and telecommunications engineers, scientists working in biology and chemistry, medical practitioners, and academics working in this field. - Provides a comprehensive review of semiconductor lasers and their applications in engineering, biology, chemistry and medicine - Discusses photonic crystal lasers, high power semiconductor lasers and laser beams, and the use of semiconductor lasers in ultrafast pulse generation - Reviews applications of visible and near-infrared emitting lasers and mid- and far-infrared emitting lasers

This volume contains the lectures and seminars presented at the NATO Ad vanced Study Institute on "Solid State Lasers: New Developments and Appli cations" the fifteenth course of the Europhysics School of Quantum Electronics, held under the supervision of the Quantum Electronics Division of the European Physical Society. The Institute was held at Elba International Physics Center, Marciana Marina, Elba Island, Tuscany, Italy, August 31 -September 11, 1992. The Europhysics School of Quantum Electronics was started in 1970 with the aim of providing instruction for young researchers and advanced students al ready engaged in the area of quantum electronics or wishing to switch to this area from a different background. Presently the school is under the direction of Professors F.T. Arecchi and M. Inguscio, University of Florence, and Prof. H. Walther, University of Munich, and has its headquarters at the National Insti tute of Optics (INO), Florence, Italy. Each time the directors choose a subject of particular interest, alternating fundamental topics with technological ones, and ask colleagues specifically competent in a given area to take the scientific responsibility for that course.

This book provides a comprehensive overview of laser sources and their applications in various fields of science, industry, and technology. After an introduction to the basics of laser physics, different laser types and materials for lasers are summarized in the context of a historical survey, outlining the evolution of the laser over the past five decades. This includes, amongst other aspects, gas lasers, excimer lasers, the wide range of solid-state and semiconductor lasers, and femtosecond and other pulsed lasers where particular attention is paid to high-power sources. Subsequent chapters address related topics such as laser modulation and nonlinear frequency conversion. In closing, the enormous importance of the laser is demonstrated by highlighting its current applications in everyday life and its potential for future developments. Typical applications in advanced material processing, medicine and biophotonics as well as plasma and X-ray generation for nanoscale lithography are discussed. The book provides broad and topical coverage of laser photonics and opto-electronics, focusing on significant findings and recent advances rather than in-depth theoretical studies. Thus, it is intended not only for university students and engineers, but also for scientists and professionals applying lasers in biomedicine, material processing and everyday consumer products. Further, it represents essential reading for engineers using or developing high-power lasers for scientific or industrial applications.

Starting from the basics of semiconductor lasers with emphasis on the generation of high optical output power the reader is introduced in a tutorial way to all key technologies required to fabricate high-power diode-laser sources. Various applications are exemplified.

Contents:Materials and Related Physics: Magnetic Field and Dimensionality Induced Population Effects in HgSe and HgSe:Fe (O Portugall et al)Growth and in Situ Scanning Tunneling Microscopy Studies of IV–VI Semiconductors (Abstract) (G Springholz)Detectors and Arrays: China's Satellite Project for Earth Observation and Infrared Detection (D-B Kuang)Recent Progress in Quantum Well Infrared Photodetectors and Focal Plane Arrays for LWIR Imaging Applications (S S Li)Infrared Lasers: Mid-Infrared Resonant-Cavity-Based Devices: Of Detectors and Emitters (J Bleuse et al)W Lasers for the Mid-IR (J R Meyer et al)Devices and Related Physics: Optoelectronic Devices from Indium Aluminium Antimonide and Mercury Cadmium Telluride (T Ashley)Three-Terminal Superconductor–Semiconductor Devices (H Takayanagi & T Akazaki)Physics: Coherent Anti-Stokes Raman Scattering in Diluted Magnetic IV–VI Epilayers and Superlattices (H Pascher et al)High Field Cyclotron Resonance in GaSb and Effective Mass at the Γ and L-Points (H Arimoto et al)Quantum Dots: Growth and Characterization of InAs Quantum Dots (N N Ledentsov)Self-Assembled InAs Quantum Boxes: Growth, Intrinsic Properties, Potential Applications (Abstract) (J M Gérard)and other papers Readership: Researchers in the field of semiconductors.

This book covers the fundamental aspects of fiber lasers and fiber amplifiers, and includes a wide range of material from laser physics fundamentals to state-of-the-art topics in this rapidly growing field of quantum electronics. This expanded and updated new edition includes substantial new material on nonlinear frequency conversion and Raman fiber lasers and amplifiers, as well as an expanded list of references inclusive of the recent literature in the field. Emphasis is placed on the nonlinear processes taking place in fiber lasers and amplifiers, their similarities, differences to, and their advantages over other solid-state lasers. The reader will learn the basic principles of solid-state physics and optical spectroscopy of laser active centers in fibers, the main operational laser regimes, and will receive practical recommendations and suggestions on fiber laser research, laser applications, and laser product development. The book will be useful for students, researchers, and professional physicists and engineers who work with lasers in the optical and telecommunications field, as well as those in the chemical and biological industries.

Recent advances in ultra-high-power lasers, including the free-electron laser, and impressive airborne demonstrations of laser weapons systems, such as the airborne laser, have shown the enormous potential of laser technology to revolutionize 21st century warfare. Military Laser Technology for Defense, includes only unclassified or declassified information. The book focuses on military applications that involve propagation of light through the atmosphere and provides basic relevant background technology. It describes high-power lasers and masers, including the free-electron laser. Further, Military Laser Technology for Defense addresses how laser technology can effectively mitigate six of the most pressing military threats of the 21st century: attack by missiles, terrorists, chemical and biological weapons, as well as difficulty in imaging in bad weather and threats from directed beam weapons and future nuclear weapons. The author believes that laser technology will revolutionize warfare in the 21st century.