Abstract
Over the past two decades, fiber laser technologies have matured to such an extent that they have captured a large portion of the commercial laser marketplace. Yet, there still is a seemingly unquenchable thirst for ever greater optical power to levels where certain deleterious light-matter interactions that limit continued power scaling become significant. In the past decade or so, the industry has focused mainly on waveguide engineering to overcome many of these hurdles. However, there is an emerging body of work emphasizing the enabling role of the material. In an effort to underpin these developments, this paper reviews the relevance of the material in high power fiber laser technologies. As the durable material-of-choice for the application, the discussion will mainly be limited to silicate host glasses. The discussion presented herein follows an outward path, starting with the trivalent rare earth ions and their spectroscopic properties. The ion then is placed into a host, whose impact on the spectroscopy is reviewed. Finally, adverse interactions between the laser lightwave and the host are discussed, and novel composition glass fiber design and fabrication methodologies are presented. With deference to the symbiosis required between material and waveguide engineering in active fiber development, this review will emphasize the former. Specifically, where appropriate, materials-based paths to the enhancement of laser performance will be underscored.
Highlights
As of the writing of this review, fiber lasers exceeding 100 kW of optical power are commercially available.1 In homage to the importance of fiber lasers, there are a number of excellent reviews that have emerged over the past decade or so.2–9 Applications for them are wide-ranging, from weapons systems10 to down-hole drilling,11 and from medicine12 to lidar.13 Well-understood to those in the field is that continuous-wave (CW) high power fiber lasers serve mainly as brightness converters
The actual ranges provided in the patent are “3 < (n1Mþn2H)/H < 20,” preferably
Summary
As of the writing of this review, fiber lasers exceeding 100 kW of optical power are commercially available. In homage to the importance of fiber lasers, there are a number of excellent reviews that have emerged over the past decade or so. Applications for them are wide-ranging, from weapons systems to down-hole drilling, and from medicine to lidar. Well-understood to those in the field is that continuous-wave (CW) high power fiber lasers serve mainly as brightness (power density) converters. Fiber lasers can efficiently be pulsed, and for reasons unique to the amorphous host, enable gain at somewhat arbitrary (and wellcontrolled) wavelengths, as may be required, for example, in spectroscopic lidar systems.. Fiber lasers can efficiently be pulsed, and for reasons unique to the amorphous host, enable gain at somewhat arbitrary (and wellcontrolled) wavelengths, as may be required, for example, in spectroscopic lidar systems.13,15,16 That being said, it is not necessarily the goal of this paper to review fiber laser applications, configurations, or requirements. One or more such deleterious interactions limit the scalability of a particular system As reviewed these can be related to, for example, nonlinear propagation effects, or even to structural changes in the glass or to the rare earth dopant. The paper concludes with future perspectives, with a major emphasis on the fabrication of fibers with less conventional compositions
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