High-stability, linearly polarized mode-locking generation from a polarization-maintaining fiber oscillator around 2.8 µm

In this Letter, a high-stability, linearly polarized mode-locked polarization-maintaining (PM) E r 3 + -doped fluoride fiber oscillator at ∼ 2.8 µ m is presented for the first time, to the best of our knowledge, where an InAs-based semiconductor saturable absorber mirror is used as the mode locker, and a film polarizer is employed for maintaining the linearly polarized oscillation. In the free-running state, stable linearly polarized mode-locked pulses ( τ = 44 p s and P = 446 m W ) at 2.795 µm, with a high polarization extinction ratio of > 23 d B and a low integrated relative intensity noise of 0.087% [1 Hz–10 MHz], have been achieved, which can be strongly immune to external mechanical perturbations. By introducing a ruled reflective diffraction grating into the cavity in a Littman configuration, the continuous wavelength tuning of the linearly polarized mode-locked pulses in the range of 2717–2827 nm is obtained as well. To the best of our knowledge, this marks the first demonstration of a linearly polarized PM fiber oscillator in the > 2.5 µ m mid-infrared region.