Efficient mid-infrared Raman soliton frequency shift in a tellurite microstructured optical fiber

We present a numerical study on efficient mid-infrared Raman soliton generation in a tellurite microstructured optical fiber with femtosecond Tm-doped fiber laser pulses as the pump source. A tunable soliton exhibits a wavelength shift of up to 3.54 mu m and a power conversion efficiency of up to 74.2% while consuming a pump peak power of no more than 1 kW at 1.96 mu m, owing to the proper design of the dispersion and nonlinearity of the tellurite fiber. We investigated the effects of pump parameters on soliton properties and found that adjusting the pump pulse duration allows for a broader tuning range of up to 3.63 mu m or a higher conversion efficiency of 94.5%. The study describes an effective means of constructing compact and efficient femtosecond tunable mid-infrared laser sources with low operation power, which will boost potential applications in the important region of above 2 mu m.