Fiber laser generating switchable radially and azimuthally polarized beams with 140 mW output power at $1.6μm$ wavelength

We report a fiber laser design that is capable of producing switchable radially and azimuthally polarized beams at $1.6μm$⁠. A c-cut calcite crystal within a three-lens telescope is inserted in the cavity of an erbium doped fiber laser design. Due to the axially symmetric birefringence of the calcite crystal, radially, and azimuthally polarized modes have spatially separated foci in the cavity. Switching between the radially and azimuthally polarized outputs can be achieved by simply translating one of the lenses of the telescope. Output power more than 135 mW for both polarizations has been obtained.