Thermally driven continuous-wave and pulsed optical vortex.

We demonstrated a continuous-wave (cw) and pulsed optical vortex with topological charges driven by heat generated during the lasing process without introducing the astigmatism effect and reducing lasing efficiency. During the lasing process, the topological charges were changeable by the thermal-induced lens and selected by the mode-matching between the pump and oscillating beams. With a graphene sample as the saturable absorber, a pulsed optical vortex was achieved at a wavelength of 1.36 μm, which identified that graphene could be used as a pulse modulator for the generation of a pulsed optical vortex. Thermally driven cw and pulsed optical vortexes should have various promising applications based on the compact structure, changeable topological charges, and specific wavelength.