Large core highly doped fiber amplifiers.

Abstract

We have demonstrated amplification of nanosecond optical pulses to the millijoule level using ytterbium-doped phosphate glass fibers. Fibers with 35 um and 49 um diameter cores produced up to 700 uJ and 2.25 mJ pulses, respectively, with pulse durations less than 10 ns. By tapering the diameter of the fiber from single-mode to multi-mode, we were able to produce output with a nearly lowest-order-mode spatial profile in 35 um-core fibers that were inherently multimode. We report on progress in five areas of amplifier development: (1) pulse energy, (2) fundamental mode propagation in multi-mode fibers, (3) phosphate glass fiber processing, (4) highly doped gain fiber modeling, and (5) amplification of single-frequency pulses at 2 um wavelength. 4 ACKNOWLEDGMENTS

Suppression of the Stimulated Brillouin and Raman Scattering in Actively Q‐switched Fiber Lasers through Temporal Pulse Shaping

“…Regarding the presence of a coupled stochastic (Langevin) equation, the system falls into the category of Stochastic PDEs [ 30 ] and may be solved using an appropriate Monte–Carlo method. We have solved the system of Equations (16)–(21) using a centered‐space‐forward‐time combinational scheme of the finite difference method (CSFT‐FDM) [ 31 ] that together with the random walk method, results in a suitable and stable Monte– Carlo algorithm. [ 30 ] It is worth pointing out that each loop of the FDM algorithm is called a realization in this method.…”