High-Efficiency, High Peak-Power, Narrow Linewidth 1.9 μm Fiber Gas Raman Amplifier

We reported here a high-efficiency, high peak-power, narrow linewidth 1.9 μm fiber gas Raman amplifier based on stimulated Raman scattering (SRS) in an H
₂
-filled antiresonance hollow-core fiber. A CW seed fiber laser near 1908 nm is amplified by the first vibrational Stokes wave of hydrogen molecules while pumping with a pulsed 1064 nm microchip laser. The seed laser significantly enhances the vibrational SRS and suppresses the rotational SRS, resulting in a record optical-to-optical conversion efficiency of ~41% (quantum efficiency ~73.5%) for such H
₂
vibrational Raman experiments in hollow-core fibers, with 1.4 m fiber and only 3 bar H
₂
, which is more preferable in applications. The maximum average Stokes power of 74.2 mW and the peak power of ~150 kW with the linewidth about 1 GHz (~12 pm) are obtained. The linewidth characteristics of such fiber gas Raman laser sources are systematically studied for the first time by experimental methods. This paper provides an effective method to obtain efficient 1.9 μm fiber sources of both high peak power and narrow linewidth.