Passively Modelocked All-PM Thulium-Doped Fiber Laser at 2.07 μm

Here we present a self-started passively mode-locked thulium-doped fiber laser with in-band pumping at 1561 nm that fully retains polarization and emits beyond 2 μ m. We obtained a sequence of light pulses at 13.084 MHz, where the pulse and spectral widths were 94 ps and 70 pm, respectively, at 2069.5 nm. The measured instantaneous angular frequency shows that these light pulses are chirp-free.