Direct generation of high-average-power mid-infrared cylindrical vector pulses from a simple polarization-maintaining fiber laser

We demonstrate watt-level average power mode-locking operations in a simple linear-cavity polarization-maintaining (PM) Er:ZBLAN fiber laser at ~2.78 µm, generating ultrafast pulses for both linearly polarized (LP) and cylindrical vector beam (CVB) modes. Self-starting mode-locking is achieved via a semiconductor saturable absorber mirror (SESAM), yielding a maximum average output power of 1.33 W in the LP mode regime. Besides, integrating a self-consistent S-waveplate into the cavity also enables the CVB mode conversion, generating 1.01 and 1.02 W average output powers for the azimuthally and radially polarized mode-locking pulses, respectively. This work presents a compact and efficient ultrafast fiber laser platform for directly generating high-power mid-infrared ultrafast structured laser emissions.