Kilowatt Ytterbium-Raman fiber laser

Abstract

A kilowatt-level Raman fiber laser is demonstrated with an integrated Ytterbium-Raman fiber amplifier architecture. A high power Ytterbium-doped fiber master oscillator power amplifier at 1080 nm is seeded with a 1120 nm fiber laser at the same time. By this way, a kilowatt-level Raman pump laser at 1080 nm and signal laser at 1120 nm is combined in the fiber core. The subsequent power conversion from 1080 nm to 1120 nm is accomplished in a 70 m long passive fiber. A 1.28 kW all-fiber Raman amplifier at 1120 nm with an optical efficiency of 70% is demonstrated, limited only by the available pump power. To the best of our knowledge, this is the first report of Raman fiber laser with over one kilowatt output.

1.5-kW Yb-Raman Combined Nonlinear Fiber Amplifier at 1120 nm

“…The maximal output power is 1655 W when 2010 W pump power launched into the amplifier and the power of 1120 nm laser is about 1521 W with optical efficiency of 75.6%, which is the highest power reported in 1100-1200 nm range. In the whole process of power scaling, the power of 1070 nm laser is less than 200 W and in the end only 96 W 1070 nm laser is residual in the output, which is lower than the result reported in [8], indicating that this configuration is more efficient. Figure 3 plots the output spectrum of the seed and spectrum at the maximal power (recorded by Optical Spectrum Analyzer, Yokogawa AQ6370C).…”

“…Finally they obtained 1.28 kW power output at 1120 nm [8]. For such configuration, due to the imperfect spliced point between the YDF and the following passive fiber, the beam quality of the output of YDFA may deteriorate, which would result in the generation of cladding mode that makes the insufficient power transfer to the Stokes wave.…”

Spectroscopic Features of Raman Gain Profiles in Single-Mode Fibers Based on Silica Glass

“…Thus, these fibers are successfully used for both fiber Raman amplifiers (FRAs) of optical signals and for FRLs [12,13]. Recently [14], an FRL with an output power of 188 kW with the use of the 70-m-long germanium fiber was reported. A high-efficiency Raman converter from 1080 nm to 1120 nm with a GeO 2 -doped fiber is a key element of such laser with the output power as high as kilowatts.…”

Theoretical treatment of modal instability in high-power cladding-pumped Raman amplifiers

“…Despite these advantages, challenges remain including suppression of higher-order Stokes and the difficulty of achieving high powers with a narrow linewidth output due to the onset of stimulated Brillouin scattering (SBS) [1][2][3][4][5]. At the kW pumping level, for good conversion efficiency, RFAs require much longer lengths than their Yb-doped fiber counterparts; thus making them more susceptible to SBS.…”