Abstract

A mode-locked laser/power-amplifier system based on Tm:Ho-doped silica fiber delivering femtosecond soliton pulses tunable from 1.972 μm to 2.15 μm with average output power up to 230 mW is reported. The master soliton oscillator and Raman shifter/amplifier were made of similar Tm/Ho fiber with length of 1.2 m and 4.5 m, respectively. Fibers with absorption of ~20 dB/m at pump wavelength of 1565 nm were core-pumped by erbium fiber laser. Tm/Ho amplifier acting as a Raman shifter is seeded with soliton fiber laser that generates 750 fs pulses with repetition rate of 50 MHz at 1972 nm, as shown in Fig. 1. Mode-locked oscillator uses Sb-based semiconductor saturable absorber with saturation fluence of 47 μJ/cm² and modulation depth of 10% derived from measured nonlinear reflectivity response plotted in Fig. 2(a). The absorber material consisted of 15 GalnSb quantmn-wells placed within a 3-λ GaSb cavity grown on the top of an 18-pairs AlAsSb/GaSb Bragg reflector. The room-temperature photoluminescence emission from the quantmn wells is peaked at 2035 nm. The distributed Bragg reflector has a reflectance of 99.8% in a wavelength range from 1850 nm to 2150 nm.

© 2007 IEEE