Fig. 1. Experimental setup of the all-fiber 1.7 μm fiber gas Raman laser

Fig. 2. Experimental results. (a) Measured transmission spectrum of the hollow-core fibers, insert is the micrograph of the hollow-core fibers’ cross section; (b)-(d) schematic of the all-fiber gas cell preparation process; (e) micrograph of fusion point 1

Fig. 3. Forward and backward output spectra at the maximum pump power. (a) Forward output spectrum without FBG, insert is the fine spectrum and the near-field pattern of 1540 nm pump light; (b) backward output spectrum without FBG; (c) forward output spectrum when adding FBG, insert is the fine spectrum and the near-field pattern of 1693 nm Stokes light; (d) backward output spectrum when adding FBG

Fig. 4. Evolution of output powers and conversion efficiency with the incident pump power. (a) Forward output residual pump light and Stokes light powers; (b) backward output pump light and Stokes light powers; (c) total Stokes light power; (d) total optical-to-optical conversion efficiency