Controlled generation of ultrafast vector vortex beams from a mode-locked fiber laser.

Abstract

We report on a new class of mode-locked fiber lasers that allow direct creation of ultrafast vector vortex beams at arbitrary positions on the higher-order Poincaré sphere. The on-demand generation of space-variant polarization patterns was realized by controlling geometric phases inside the laser resonator to map polarization to orbital angular momentum. Thanks to the special cavity design, the required intracavity manipulation of the geometric phase imposed no disturbance on the passively mode-locked operation, thus demonstrating robust and flexible switching of vectorial modes with an 8.5ps pulse duration. Analytical expressions were deduced to model the generated cylindrically symmetric polarization profiles, which are in agreement with experimental observations. The presented fiber laser would constitute a compact light source for producing ultrafast pulses in high-purity structured modes, which may find broad applications in classical and quantum optics.