Supercontinuum generation and lasing in thulium doped tellurite microstructured fibers

We report supercontinuum (SC) generation in Tm³⁺ doped tellurite microstructured fibers (TMFs) pumped by a 1.56 μm femtosecond fiber laser. In comparison with SC generation in undoped TMFs, the SC spectral bandwidth and the spectral intensity in the wavelength region of >1.9 μm are evidently enlarged in Tm³⁺ doped TMFs owing to the contribution of the combination of linear gain of Tm³⁺ and the nonlinear optical effects to spectral broadening. Furthermore, a transition from SC generation to 1.887 μm lasing (Tm³⁺: ³F₄→³H ₆ transition) is observed in Tm³⁺ doped TMFs by varying the pulse width of the pump laser from 0.29 to 3.47 ps, which gives the evidence of the above spectral broadening mechanism. This is the first observation of the transition from SC generation to lasing, to the best of our knowledge.