The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

High power fiber lasers: current status and future perspectives [Invited]

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

The Eu3+ charge transfer energy and the relation with the band gap of compounds

The pulsed laser deposition is a new technique for the growth of thin films,which has been attended generally by people recently The physical principle, unique characteristics and the proceeding of the study were introduced briefly In addation, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was describedPULS

Pulsed laser deposition of thin films

After a brief examination of known insulating laser crystals and the stimulated emission channels of their generating activator ions, this article reviews recent advances in the development of novel lasing crystals and ceramics, as well as inorganic and organic nonlinear-laser crystals for χ(3) and cascaded χ(3) ↔ χ(2) frequency converters Several new modern attractive technologies in the physics and techniques of crystalline lasers are also discussed

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.200710008

Laser crystals and ceramics: recent advances

Applications requiring long-range atmospheric propagation are driving the development of high-power thulium fiber lasers. We report on the performance of two different laser configurations for high-power tunable thulium fiber lasers: one is a single oscillator utilizing a volume Bragg grating for wavelength stabilization; the other is a master oscillator power amplifier system with the oscillator stabilized and made tunable by a diffraction grating. Each configuration provides >150W of average power, >50% slope efficiency, narrow output linewidth, and >100nm tunability in the wavelength range around 2μm.

High-power widely tunable thulium fiber lasers

Single mode laser action in a diode-pumped gain-guided, index- antiguided Nd3+-doped phosphate glass fiber having a 200-μm-diameter core is demonstrated. Near-Gaussian beam quality was maintained, even when pumped up to four times the threshold pump power, indicating robust lowest order mode oscillation. Subtle differences associated with the effectiveness of diode pumping gain-guided, index-antiguided fibers are discussed.

Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser

A comparison of Tm,Ho:YLF; Tm,Ho:LuLF; and Tm,Ho:LuAG crystals under identical experimental conditions showed that Tm,Ho:LuLF yielded significantly better performance. The thermal expansion coefficients were measured. These crystals were experimentally characterized in the spectral region of 680 nm and 780 nm accessible to laser diodes. The effective energy storage lifetimes of the Ho 5I7 manifold at room temperature were measured experimentally. At 10 Hz and 273 K, free-running laser output energy in excess of 17 mJ was obtained in Tm,Ho:YLF compared with 30 mJ in Tm,Ho:LuLF and 24.4 mJ in Tm,Ho:LuAG. The slope efficiencies with respect to the incident pump energy were 7.4%, 12.9%, and 11.6%, respectively. The temperature dependence of the output energies of these lasers was investigated.

Spectroscopic and diode-pumped-laser properties of TM,Ho:YLF; Tm, Ho:LuLF; and Tm,Ho:LuAG crystals: a comparative study

The authors report laser oscillation in what appears to be a single transverse mode with very large mode area in optical fibers having heavily Nd-doped 100μm diameter cores with refractive index significantly lower in the core than in the surrounding cladding. Since fibers of this type cannot support conventional index-guided modes, their results appear to confirm a recent analysis which predicts gain-guided single-mode propagation in index antiguided fibers, provided the gain coefficient in the core exceeds a threshold value. Fibers of this type may be of significant interest for amplifiers and oscillators having large power outputs and/or small nonlinear pulse distortion.

/pdf/confined-propagation-and-near-single-mode-laser-oscillation-1ypzsa6ie1.pdf

Confined propagation and near single-mode laser oscillation in a gain-guided, index antiguided optical fiber

Lowest-order, single-mode laser oscillation is reported in gain-guided index-antiguided fiber lasers having core diameters from 100 to 400 μm. A model is presented explaining how to select resonator mirrors to assure single-mode operation.

Vikas Sudesh

Papers

High-power widely tunable thulium fiber lasers

Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser

Spectroscopic and diode-pumped-laser properties of TM,Ho:YLF; Tm, Ho:LuLF; and Tm,Ho:LuAG crystals: a comparative study

Confined propagation and near single-mode laser oscillation in a gain-guided, index antiguided optical fiber

Very large-core, single-mode, gain-guided, index-antiguided fiber lasers.