Novel Raman Fiber Lasers Emitting in the U-Band With Combined Volume Bragg Gratings

Narrow linewidth and widely tunable high-power Raman fiber lasers emitting in the U-band wavelength were demonstrated based on combinations of volume Bragg gratings with different center wavelengths. The narrowed linewidth was 65 pm at a center wavelength of 1657.86 nm with a maximum output power of 8.3 W, corresponding to a slope efficiency of 55.6%. For the tunable Raman fiber laser, continuously tunable dual-wavelength emission was obtained in a wide band (1621.3-1683.5 nm) with a wavelength difference over 60 nm (0.7-62.2 nm). The maximum output power was 11 W, corresponding to a slope efficiency of 76.6%.