Advances in High-Power Fiber and Diode Laser Engineering
Advances in High-Power Fiber and Diode Laser Engineering provides an overview of recent research trends in fiber and diode lasers and laser systems engineering. In recent years, many new fiber designs and fiber laser system strategies have emerged, targeting the mitigation of different problems which occur when standard optical fibers are used for making high-power lasers. Simultaneously, a lot of attention has been put to increasing the brightness and the output power of laser diodes. Both of these major laser development directions continue to advance at a rapid pace with the sole purpose of achieving higher power while having excellent beam quality. The book begins by introducing the principles of diode lasers and methods for improving their brightness. Later chapters cover quantum cascade lasers, diode pumped high power lasers, high average power LMA fiber amplifiers, high-power fiber lasers, beam combinable kilowatt all-fiber amplifiers, and applications of 2 μm thulium fiber lasers and high-power GHz linewidth diode lasers. Written by a team of authors with experience in academia and industrial research and development, and brought together by an expert editor, this book will be of use to anyone interested in laser systems development at the laboratory or commercial scale.
Inspec keywords: brightness; quantum cascade lasers; semiconductor lasers; fibre lasers; optical pumping; laser beams; quantum well lasers; laser materials processing; optical fibre amplifiers; spectral line breadth
Other keywords: diode pumped high power lasers; high average power large mode area fiber amplifiers; GHz linewidth diode lasers; diode laser brightness improvement; quantum cascade lasers; directed energy; diode laser engineering; laser diode beam combining; kilowatt all fibre laser amplifiers; high-power fiber lasers; thulium fibre laser materials processing; laser pumping
Subjects: Laser materials processing; Textbooks; Design of specific laser systems; Laser beam interactions and properties; General electrical engineering topics; Laser beam characteristics and interactions; Fibre lasers and amplifiers; Semiconductor lasers; Laser materials processing; Lasing action in semiconductors; Fibre lasers and amplifiers
- Book DOI: 10.1049/PBCS054E
- Chapter DOI: 10.1049/PBCS054E
- ISBN: 9781785617515
- e-ISBN: 9781785617522
- Page count: 401
- Format: PDF
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Front Matter
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1 Diode laser: fundamentals and improving the brightness
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This chapter is dedicated to briefly looking back at the evolution of rise of a disruptive technology and surveying the current challenges and roadblocks to improving brightness as well as understanding the current state-of-the-art of diode lasers followed by a summary of outlook of its brightness improvement.
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2 Coherent beam combining architectures for high-power laser diodes
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In this chapter, high-power direct diode laser systems are becoming more and more attractive for industrial applications where they are not limited anymore to the pumping of solid-state lasers and fibres. Nonetheless, the highest power emitted from a single laser chip is typically below 20 W for a broad area element in the near infrared, and even below in other spectral ranges. Thus the high powers required for cutting, welding and other advanced manufacturing techniques are only available by combining multiple emitters in a single beam - strength lies in numbers in this matter too!
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3 High-power laser diodes for direct applications and laser pumping
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This chapter focuses primarily on progress in HPDLS that are grown on GaAs substrates and emit in the operating wavelength range λop = 900... 1000 nm, where the highest performance is reported, and the majority of studies are performed. Our discussion starts with a review of progress in broad area BA-HPDLs that reach the very highest powers and efficiencies, at the cost of degraded beam quality.
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4 Quantum cascade lasers
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In this chapter, we present a brief overview of the QCL technology with an emphasis on the commercially important 3 μm to 12 μm spectral region covering the infrared fingerprint spectral region and the two infrared atmospheric windows (3 to 5 μm and 8 to 12 μm). Specifically, laser core design, waveguide design, and various aspects of mode control for QCLs are discussed below.
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5 Diode pumped high power lasers
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In this chapter, we will guide the reader through development process of high average power diode pumped solid-state lasers, starting from material choice, through amplifier geometry and detailed description of the lasers at HiLASE.
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6 High average power large mode area (LMA) fiber amplifiers
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This chapter is devoted to summarizing the current state of industrial fiber lasers and focusing on the key challenges to extending the power levels of combinable narrowband fiber amplifiers to many multikilowatts suitable for Directed Energy application.
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7 Optical fibers for high-power operation
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Optical fibers have demonstrated, against all early predictions, that their geometry is extremely well-suited for handling high optical powers. However, over the years, many refinements have been done to the basic structure of these waveguides to allow guiding and generating high-powers. As a result of this development the fibers employed in high-power laser systems differ significantly from those typically used in other fields such as telecommunications and/or sensors. Therefore, this chapter is devoted to describing and explaining the main intricacies of those optical fiber designs presently used for high-power operation. In this context, the main goal of this chapter is that the reader gets an overview of the different fiber designs and building blocks of high-power optical fibers. The chapter is divided into three main parts: a brief historical overview of the evolution of this technology, a description of the main constituents of fibers for high-power operation (including the core, the pump cladding and materials), and, finally, an outlook in which novel trends in the design of these waveguides are briefly described.
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8 High power fiber lasers
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This review concentrates on the progress and developments that have led to explosive growth in high power continuous wave (CW) fiber lasers over the last decade. Here we arbitrarily defined high power fiber operation as being close to a single mode in beam output with powers in the kilowatt range. This growth has largely been led by Yb fiber lasers up to now. However, in this review, we also highlight the potential for high power, high brightness operation of two alternative approaches, thulium fiber lasers that operate at 2 mm wavelength, and CW Raman fiber lasers (RFLs), which have yet to reach kW power levels.
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9 Beam combinable, kilowatt all-fiber amplifiers for directed energy
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In this chapter, several beam combining architectures suitable for DE applications have been reported, and are divided into two distinct categories: incoherent beam combination (IBC) and coherent beam combination (CBC). The purpose of each method is to increase the far field intensity when brightness and power of a single fiber amplifier is limited. In IBC, an array of fiber lasers is superimposed in the far field without control of the relative spectra or phases of the different fibers. No brightness enhancement is obtained from this method, limiting the maximum intensity in the far field. Although such beam combining has been successfully demonstrated by the Navy [5], this approach is limited to propagation ranges on the order of a few kilometers. In spectral beam combining (SBC), a separate class of IBC, incoherent beams of different wavelengths are spatially overlapped to create a single output beam of multiple colors. The brightness of the propagating beam can be increased at the cost of increased spectral bandwidth. Similarly, SBC has the advantage of not requiring active phase control or mutual temporal coherence of the individual beams. Alternatively, coherent beam combining (CBC) schemes require proper phase, frequency, and polarization relationships for efficient beam combination. Overall, due to their brightness enhancements, for longer range and higher power/ intensity DE applications, SBC and CBC are potentially more appealing.
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10 Applications of high-power 2 m thulium fiber lasers in materials processing
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Recent advances in the development of high-power laser sources emitting at the wavelength around 2 mm have enabled a novel material processing regime that is currently finding many new industrial and scientific applications, from automotive manufacturing and biomedical engineering to microelectronics and infrared photonics. High output powers and system reliability enabled by a robust fiber laser architecture bring many new opportunities to laser materials processing community, but also many scientific and technical challenges. On the one hand, a large number of new and unique processes have been introduced, from absorber-free welding of transparent polymers and volume-selective micro-processing of semiconductors to local refractive index modifications in infrared optical materials. On the other hand, with a steadily growing selection of commercially available continuous-wave (CW) and pulsed thulium-doped fiber lasers, processing limits for many conventional laser processing techniques such as cutting, drilling, and welding, will need to be reassessed. In addition, the knowledge of materials' response to irradiation at 2 mm is still incomplete for many important classes of materials, and a limited availability of beam delivery equipment optimized for this wavelength makes industrial implementation of thulium fiber lasers challenging. This chapter is aiming at improved understanding of fundamental principles of light-matter interaction at 2 mm, discusses various new applications, and contributes to implementation of thulium fibers lasers as a promising tool for many industrial areas.
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11 High-power GHz linewidth diode lasers and their applications
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This chapter will discuss the development and applications of semiconductor laser systems with output reaching several hundred watts and with spectral widths of the emission down to 10 GHz.
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Back Matter
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