Broadband soliton self-frequency shifting of hybrid femtosecond Er/Tm fiber laser system in microstructured suspended-core tellurite fiber

In this study, we propose a widely tunable in the 1.6-2.65 mu m range femtosecond fiber laser source, generating high-quality sech-shaped pulses with the duration of order 100 fs. Experimental setup contains hybrid all-fiber Er/Tm pump laser generating 150 fs pulses of 2 nJ in Erbium (1.56 mu m) channel and 125 fs pulses of 4 nJ in Thulium (2 mu m) channel respectively. This laser source was coupled to a 50 cm piece of suspended- core microstructured TeO2-WO3-La2O3 glass fiber with launching efficiency of about 10%. We have observed Raman self-frequency shifting solitons in this fiber with maximum red shift of 2.25 mu m for Erbium channel and 2.65 mu m for Thulium channel. By varying energy of pump pulses, solitons can be tuned in broadband spectral region. We have made theoretical studies of nonlinear pulse dynamics in the tellurite fiber with carefully measured and calculated parameters. Numerical simulation is in a very good agreement with the experiment