18 W single-stage single-frequency acoustically tailored Raman fiber amplifier

A single-mode polarization-maintaining fiber doped to increase the Raman gain while suppressing stimulated Brillouin scattering (SBS) was utilized in a single-stage counter-pumped Raman fiber amplifier. The SBS suppression was achieved through the acoustic tailoring of the core. A pump probe experiment was conducted to characterize the Brillouin gain and indicated the existence of multiple Brillouin peaks. When the amplifier was seeded with approximately 15 mW of 1178 nm light, 11.5 W of cw output power was obtained with a linewidth ≤2 MHz. The application of a thermal gradient to further mitigate the SBS process increased the output power to 18 W, thus providing a net amplifier gain >30 dB.