We have demonstrated a monolithic (fully fused), 1.2-kW, Yb-doped fiber laser with near-single-mode beam quality. This laser employs a new generation of high-brightness, fiber-coupled pump sources based on spatially multiplexed single emitters, with each pump providing 100 W at 915 nm within 0.15 NA from a standard 105/125 μm fiber. The fiber laser is end pumped through the high-reflector FBG using a 19:1 fused-fiber pump combiner, eliminating the need for pump/signal combiners. The output wavelength is 1080 nm, with a linewidth of < 0.5 nm FWHM. A peak power of 1.5 kW was reached in modulated operation (1-ms pulse duration) with M 2 < 1.2.
We report modeling and experimental results that demonstrate mechanisms limiting the output power of semiconductor lasers and a method experimentally yielding a dramatic increase of the maximum continuous wave output power. Unfolded cavity is used to achieve higher power and efficiency by improving the alignment between the carrier and photon density profiles in a long cavity device. This method offers reduced longitudinal spatial hole burning (LSHB) and lower photon density inside the laser cavity; therefore, it decreases possible LSHB and non-linear effects that could limit the output power of a semiconductor laser. We have demonstrated 29.5W output from 5.7mm long and 100um wide waveguide at 9xx nm using an unfolded cavity. A semiconductor laser with an unfolded cavity allows scaling of the output power by increasing the cavity length.
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