High-power Raman soliton generation tunable from 1.76 to 1.84 µm in all-fiber polarization-maintaining erbium-doped amplifier

An all-fiber polarization maintaining laser system of wavelength tunable from 1.76 to 1.84 μm based on the Raman-induced soliton self-frequency shift in an erbium-doped amplifier is demonstrated. The system only includes oscillator and two-stage amplifiers which are built entirely based on commercial silica fibers and devices. The ultra-short pulse achieved by oscillator and first amplifier stage by the method of nonlinear compression is delivered into second amplifier stage which is designed as both Raman shifter and amplifier. Within the pump power range of 16-25 W, tunable Raman soliton can be obtained with the average power gradually increases from ~180 mW to ~250 mW as the center wavelength of the soliton shifts towards the longer wavelength direction within the range of 1.76 to 1.84 μm. The system delivers Raman soliton from an entirely fiberized, fusion spliced system without any free-space optics, which can provide robust and stable soliton generation. To our knowledge, this tunable soliton source is the highest output power demonstrated within 1.7-1.8 μm wavelength range from an all-fiber polarization maintaining laser. Our experiment provides a feasible femtosecond source for multiphoton microscopy.