In this paper, we summarize the fundamental properties and review the latest developments in high power fiber lasers. The review is focused primarily on the most common fiber laser configurations and the associated cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancement observed in single-mode and multimode high power fiber lasers. The review includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, transverse modal instabilities and photodarkening. Finally, the paper summarizes the power evolution in continuous-wave and pulsed ytterbium-doped fiber lasers and their impact on industrial applications.

High Power Fiber Lasers: A Review

Random distributed feedback fibre lasers

In this review paper, we present radiation effects on silica-based optical fibers. We first describe the mechanisms inducing microscopic and macroscopic changes under irradiation: radiation-induced attenuation, radiation-induced emission and compaction. We then discuss the influence of various parameters related to the optical fiber, to the harsh environments and to the fiber-based applications on the amplitudes and kinetics of these changes. Then, we focus on advances obtained over the last years. We summarize the main results regarding the fiber vulnerability and hardening to radiative constraints associated with several facilities such as Megajoule class lasers, ITER, LHC, nuclear power plants or with space applications. Based on the experience gained during these projects, we suggest some of the challenges that will have to be overcome in the near future to allow a deeper integration of fibers and fiber-based sensors in radiative environments.

Radiation Effects on Silica-Based Optical Fibers: Recent Advances and Future Challenges

Optical fibers with the bismuth show promise for developing efficient fiber lasers and amplifiers in extended bands of near IR region, in particular, through a whole spectral range of 1150–1550 nm. Devices capable of operating in this region are required for applications in advanced optical communications, medicine and astrophysics, among others. In this paper, Evgeny Dianov from the Fiber Optics Research Center of the Russian Academy of Sciences in Moscow reviews the luminescent properties and light-emitting mechanisms of bismuth-doped fibres and the progress made towards constructing lasers and amplifiers from such fibers. In particular, the author describes a laser emitting at 1460 nm with a conversion efficiency of 50%, and an amplifier with a peak gain of 24 dB at 1427 nm, a 3 dB bandwidth of 36 nm and a noise figure of 6 dB.

/pdf/bismuth-doped-optical-fibers-a-challenging-active-medium-for-4mys86cj53.pdf

Bismuth-doped optical fibers: a challenging active medium for near-IR lasers and optical amplifiers

The recent results on the new laser material – Bi-doped glasses and optical fibers are reviewed. First, luminescence properties of various Bi-doped glasses are discussed. At last the results of investigations of Bi-doped fiber lasers covering a wavelength range of 1150 – 1550 nm are presented.

https://iopscience.iop.org/article/10.1002/lapl.200910025/pdf

Bi-doped fiber lasers

Optical fibers with bismuth-doped silicate and germanate glass cores were fabricated by the modified chemical vapor deposition technique (solution and vapor-phase Bi incorporation) The fibers revealed an efficient luminescence with a maximum in the 1050-1200 nm spectral range, FWHM up to 200nm, and a lifetime of the order of 1ms

Bismuth-doped-glass optical fibers—a new active medium for lasers and amplifiers

For the first time, 3-dimensional luminescence spectra (luminescence intensity as a function of the excitation and emission wavelengths) have been obtained for bismuth-doped optical fibers of various compositions in a wide spectral range (450-1700 nm). The bismuth-doped fibers investigated have the following core compositions: SiO2, GeO2, Al-doped SiO2, and P-doped SiO2. The measurements are performed at room and liquid nitrogen temperatures. Based on the experimental results, the positions of the low-lying energy-levels of the IR bismuth active centers in SiO2- and GeO2-core fibers have been determined. Similarity of the energy-level schemes for the two core compositions has been revealed.

Combined excitation-emission spectroscopy of bismuth active centers in optical fibers

The authors propose a new simple configuration for 1.24 and 1.48 /spl mu/m Raman fibre lasers which are promising pumping sources for 1.31 /spl mu/m Raman amplifiers and Er-doped fibre amplifiers, respectively. Efficient resonant conversion of CW 1.06 /spl mu/m radiation to the first (1.24 /spl mu/m) and second (1.48 /spl mu/m) Raman Stokes in a phosphosilicate fibre is demonstrated for the first time.

CW high power 1.24 [micro sign]m and 1.48 [micro sign]m Raman lasers based on low loss phosphosilicate fibre

We report a laser-diode-pumped 1407-nm Raman fiber laser with an output power of 1 W. In this three-cascaded cw Raman laser, based on a single active phosphorus-doped silica fiber, for the first time to the authors’ knowledge successive generation of Stokes components of essentially different frequency shifts (1330 and 490 cm-1) has been realized. These Stokes components are associated with both constituents (P2O5 and SiO2) of the fiber core glass.

/pdf/three-cascaded-1407-nm-raman-laser-based-on-phosphorus-doped-3s4jv1x27w.pdf

I. A. Bufetov

Papers

Bi-doped fiber lasers

Bismuth-doped-glass optical fibers—a new active medium for lasers and amplifiers

Combined excitation-emission spectroscopy of bismuth active centers in optical fibers

CW high power 1.24 [micro sign]m and 1.48 [micro sign]m Raman lasers based on low loss phosphosilicate fibre

Three-cascaded 1407-nm Raman laser based on phosphorus-doped silica fiber.