Pulsed all-fiber gas Raman laser oscillator based on hollow-core photonic crystal fibers

Abstract

Fiber gas Raman laser based on hollow-core photonic crystal fibers has recently attracted enormous interest due to the giant gas Raman shift and relatively low Raman threshold. However, almost all fiber gas Raman lasers are single-pass structure, and have been demonstrated by free-space coupling of the pump light through bulky gas cells. Here, we have reported a pulsed all-fiber gas Raman laser oscillator. The resonant cavity is formed by splicing solid-core fibers and a 50- meter-long hydrogen-filled hollow-core photonic crystal fiber and further introducing homemade fiber Bragg gratings at the Stokes wavelength. Pumping by a homemade pulsed 1540 nm fiber amplifier with the pulse width of 30 ns, efficient Stokes wave at 1693 nm is obtained by pure rotational stimulated Raman scattering of hydrogen. When the repetition frequency is 3 MHz, the maximum Stokes power of 1.2 W is achieved, corresponding the optical-optical efficiency inside hollow-core photonic crystal fiber of 42.7%. Moreover, it is observed that the Raman threshold obviously decreases when the repetition frequency is consistent with the resonant frequency of the resonant cavity. This work provides good guidance for achieving all-fiber structure and low-threshold pulsed fiber gas Raman lasers, which is significant for the development and application of fiber gas Raman lasers.