Octave-spanning coherent supercontinuum generation in a step-index tellurite fiber and towards few-cycle pulse compression at 2 μ m

We experimentally demonstrate 140-THz bandwidth (at −20 dB) supercontinuum generation in a 10 cm-long all-normal dispersion step-index tellurite fiber pumped by a turn-key femtosecond fiber laser emitting at 2 . 11 μ m at a repetition rate of 19 MHz. The soliton self-frequency shifted thulium-doped fiber mode-locked laser emits initial transform-limited pulses, with 85-fs pulse duration, that are subsequently quasi-linearly chirped (over more than 50 THz) during the above nJ-level nonlinear propagation. Moreover, we numerically demonstrate the possible pulse compression down to 12 fs by means of additional linear propagation in a standard step-index fluoride fiber with anomalous dispersion.