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17 February 2010 Spectral beam combining of thulium fiber laser systems
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Beams from three frequency stabilized master oscillator power amplifier (MOPA) thulium fiber laser systems were spectrally beam combined using a metal diffraction grating. Two of the laser oscillators were stabilized with guided mode resonances filters while the third was stabilized using a gold-coated diffraction grating. Each system was capable of producing a minimum of 40 W output powers with slope efficiencies between 50-60 %. The three lasers undergoing combination were operating at wavelengths of 1984.3, 2002.1, and 2011.9 nm with spectral linewidths between 250-400 pm. Beam combining was accomplished by spatially overlapping the spectrally separated beams on a water-cooled gold-coated diffraction grating with 600 lines/mm. Beam quality measurements were completed using M2 measurements at multiple power levels of the combined beam. Power levels of 49 W were achieved before thermal heating of the metal diffraction grating cause degradation in beam quality. The combining grating was ~66% efficient for the unpolarized light corresponding to a total optical-to-optical efficiency of 33% with respect to launched pump power.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
R. Andrew Sims, Christina C. C. Willis, Pankaj Kadwani, Timothy S. McComb, Lawrence Shah, Vikas Sudesh, Zachary Roth, Menelaos Poutous, Eric G. Johnson, and Martin Richardson "Spectral beam combining of thulium fiber laser systems", Proc. SPIE 7580, Fiber Lasers VII: Technology, Systems, and Applications, 75801Q (17 February 2010);

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