This thesis is related to the spectroscopic and optical properties of doped optical fibers used as a laser amplifier for short laser pulses at high repetition rates emitting around 2 μm. Therefore short pulses created by a laser diode are amplified in thulium-doped optical fibers combining the benefits of a direct electronic control of the laser diodes' parameters and the robust setup of an optical fiber system that can easily be integrated. After the development of a high-current pulse generator especially adapted to the 2 μm laser diodes used, pulses of > 7 ns with peak powers in the Watt range could be generated. Due to the modal behaviour of these laser diodes only 2 mW of peak power could be launched into a single-mode fiber. By comparing different fiber glasses, a heavy metal fluoride glass could be identified as the optimum host for the ions thulium and holmium emitting around 2 μm. Due to the development of a numerical simulation tool based on rate equations and radiation transport equations the fiber parameters such as core diameter, fiber length etc. could be optimized, minimizing the amplified spontaneous emission (ASE) created inside the fiber. Based on this simulation a laser system consisting of cascaded fiber amplifiers could be realized. I emits short laser pulses (20-30 ns) at high repetition rates (up to 125 kHz) and peak powers of up to 5 kW. In contrast to Q-switched lasers the pulse width created is independent of the repetition rate. By using these pulses at 1.87 μm as an optical pump for a Cr2+:ZnSe laser, efficiencies of up to 22% could be reached at an emission wavelength of 2.5 μm.

The goals of this work are, first, to determine different parameters of rare-earth-doped fibers and glasses and, second, to develop a simulation model for rare-earth-doped fiber lasers and amplifiers in order to avoid time consuming and expensive measurements in the laboratory during the development of such devices. The model should be applicable to arbitrary rare earth devices in a variety of configurations and cover their steady-state and transient behavior. Moreover, cross relaxation processes between two different rare earth ions should be taken into account as it is commonly used for better performance of fiber lasers and amplifiers. For the simulation a couple of spectroscopic parameters are needed, which have to be obtained in advance from bulk glasses. Some parameters like the non-radiative transition rates are difficult to obtain and thus an approach is shown to fix these usually unknown values and to consider thermally coupled energy levels. After a short introduction, which includes general laser theory and an overview of some selected solid-state and semiconductor laser systems, some properties of rare-earth-doped materials and glass hosts are discussed. The focus is Pr3+/Yb3+-doped fluoride glass and the underlying avalanche upconversion process. Then, a coherent reflectometric technique (C-OFDR) is applied to characterize thulium-doped fluoride fiber amplifiers (TDFAs) operating in the S-band of optical communications. The optimum length of the fluoride fiber and quantities like fiber gain and optimum gain-length ratio are determined for ZBLAN fibers with different thulium concentrations. Furthermore, a frequency transfer function (FTF) method is introduced to extract fluorescent lifetimes of energy levels of arbitrary rare-earth-doped glasses and fibers from phases and/or magnitudes of the measured frequency transfer function. This method is applied to measure lifetimes of the upper laser levels of praseodymium-doped fluoride glasses, namely ZBLAN and IBZP. Some of the glass samples are co-doped with ytterbium. These results are reported together with the investigation of the concentration quenching effect. Moreover, spectroscopic results of Pr3+- and Yb3+-doped ZBLAN glasses are presented and included in the simulation model developed. Simulations are carried out for Yb3+-, Pr3+- and Pr3+/Yb3+-doped ZBLAN fiber lasers. Their behavior in stationary and dynamic states is investigated for a simple Fabry-Perot setup. The demonstration of the dominant role of the avalanche upconversion process for Pr3+/Yb3+-doped ZBLAN fiber lasers is shown and the turn-on behavior of the above mentioned lasers shows relaxation oscillations typical to solid-state lasers. With the model at hand it is easily possible to simulate any other laser or amplifier configuration as well.

DescriptionThis book provides a detailed overview of the evolution of undersea communications systems, with emphasis on the most recent breakthroughs of optical submarine cable technologies based upon Wavelength Division Multiplexing, optical amplification, new-generation optical fibers, and high-speed digital electronics. The role played by submarine-communication systems in the development of high-speed networks and associated market demands for multiplying Internet and broadband services is also covered.Importance of This TopicThis book will fill the gap between highly specialized papers from large international conferences and broad-audience technology review updates. The book provides a full overview of the evolution in the field and conveys the dimension of the large undersea projects. In addition, the book uncovers the myths surrounding marine operations and installations in that domain, which have remained known so far to only very few specialists.

From basic physics to new products, Silica Optical Fiber Technology for Device and Components examines all aspects of specialty optical fibers. Moreover, the inclusion of the latest international standards governing optical fibers enables you to move from research to fabrication to commercialization. • Reviews all the latest specialty optical fiber technologies, including those developed for high capacity WDM applications; broadband fiber amplifiers; fiber filleters based on periodic coupling; fiber branching devices; and fiber terminations • Discusses key differences among single mode fibers, multimode fibers for high speed Ethernet LAN, and dispersion compensating fibers for long-haul applications • Compares the most recently developed conventional optical fibers with the latest photonic crystal fibers still in development A self-contained, menu-driven software program is included for optical fiber design, simulating waveguide structures for most of the fibers discussed in the book.

An important guide to the major techniques for generating coherent light in the mid-infrared region of the spectrum Laser-based Mid-infrared Sources and Applications gives a comprehensive overview of the existing methods for generating coherent light in the important yet difficult-to-reach mid-infrared region of the spectrum (2–20 μm) and their applications. The book describes major approaches for mid-infrared light generation including ion-doped solid-state lasers, fiber lasers, semiconductor lasers, and laser sources based on nonlinear optical frequency conversion, and reviews a range of applications: spectral recognition of molecules and trace gas sensing, biomedical and military applications, high-field physics and attoscience, and others. Every chapter starts with the fundamentals for a given technique that enables self-directed study, while extensive references help conduct deeper research. Laser-based Mid-infrared Sources and Applications provides up-to-date information on the state-of the art mid-infrared sources, discusses in detail the advancements made over the last two decades such as microresonators and interband cascade lasers, and explores novel approaches that are currently subjects of intense research such as supercontinuum and frequency combs generation. This important book: • Explains the fundamental principles and major techniques for coherent mid-infrared light generation • Discusses recent advancements and current cutting-edge research in the field • Highlights important biomedical, environmental, and military applications Written for researchers, academics, students, and engineers from different disciplines, the book helps navigate the rapidly expanding field of mid-infrared laser-based technologies.

As the editor, I feel extremely happy to present to the readers such a rich collection of chapters authored/co-authored by a large number of experts from around the world covering the broad field of guided wave optics and optoelectronics. Most of the chapters are state-of-the-art on respective topics or areas that are emerging. Several authors narrated technological challenges in a lucid manner, which was possible because of individual expertise of the authors in their own subject specialties. I have no doubt that this book will be useful to graduate students, teachers, researchers, and practicing engineers and technologists and that they would love to have it on their book shelves for ready reference at any time.