ABSTRACT
Four actively phase-locked beams produced by fiber amplifiers in a master oscillator power amplifier (MOPA) configuration were coherently combined in a glass capillary re-imaging waveguide producing more than 100 W of coherent output with 80% combining efficiency and excellent beam quality. The beam combiner components maintained a temperature below 30 degrees C with no external cooling at >100 W of combined power.
Subject(s)
Fiber Optic Technology/instrumentation , Fiber Optic Technology/methods , Lasers , Light , Optical Fibers , Equipment Design , Hot Temperature , PolymersABSTRACT
We demonstrate passive combination of multiple beams in an optical fiber via stimulated Brillouin scattering (SBS). Four off-axis beams are combined in a long multimode optical fiber using a novel all-optical mount. The combined beam has the high spatial coherence properties of the LP(01) mode owing to the beam cleanup properties of SBS. The threshold for SBS when off-axis pumps are used is shown to be a factor of 13 times higher than for on-axis pump beams. We propose this method would improve the brightness of an array of fiber amplifiers.
ABSTRACT
We report using a Raman fiber laser (RFL) based on a multimode graded-index fiber as a novel method for beam combination of two continuous wave pump beams. Due to stimulated Raman scattering, the RFL generates a Stokes beam which can be up to 300% brighter than the pump beams. Up to 5.8 W of Stokes power is generated with an optical conversion efficiency of 56%.
ABSTRACT
Beam cleanup via stimulated Raman scattering in multimode fibers is modeled by numerically considering the competition between the Stokes modes of graded-index and step-index fibers. The relative gain of each Stokes mode is calculated by considering the overlap the various pump and Stokes modes of the fibers. Mode competition in a graded-index fiber favors the LP(01) Stokes mode while mode competition in a step-index fiber does not favor the LP(01) Stokes mode. This model explains why beam cleanup has only been reported for graded-index fibers and not for step-index fibers.
Subject(s)
Models, Theoretical , Optical Fibers , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Reproducibility of Results , Scattering, Radiation , Sensitivity and SpecificityABSTRACT
We demonstrated the successful combination and cleanup of four laser beams via stimulated Raman scattering (SRS) using a multi-port fiber combiner and a large multimode fiber. Multiple Stokes orders were observed in the output, but loss at longer wavelengths reduced the transmission of the higher Stokes orders and limited the SRS conversion efficiency. SRS beam cleanup was also investigated using a single laser beam. The output beam had a measured M(2) better than 2 for fiber lengths from 400-1400 meters.
ABSTRACT
Phasing of two-channel cw master-oscillator-power-amplifier beams by using a phase-conjugate mirror has been demonstrated for the first time to the best of our knowledge. Phasing was achieved with two fiber amplifiers in conjunction with a single-frequency Nd:YAG master oscillator by using a fiber phase-conjugate mirror in a double-pass geometry. The successful demonstration of phasing of two cw amplifier beams with a fiber phase-conjugate mirror greatly enhances the prospects for phasing of multiple laser amplifiers without complex servo-loop control systems.
