Controllable laser output of high-quality cylindrical vector beam through intra-cavity mode conversion

We experimentally demonstrate the controllable laser output of cylindrical vector (CV) beams, which feature flexibility, high efficiency, and good beam quality. Particularly, the CV laser beams have negligible radial components, distinguishing themselves from the extra-cavity-generated CV beams. The output state is controlled by an intra-cavity vortex half-wave plate (VWP). By changing the topological charge (l) of VWP, we produce l = 1 and l = 2 CV beams for example. Through rotating the half-wave plate inside the cavity, the laser outputs arbitrary CV beams around the equator of the corresponding high-order Poincaré spheres. For l = 1 and l = 2 CV beams, the polarization purities are as high as 97.8% and 96.7%, the sloping efficiencies are 15.5% and 5.4%, and the beam quality factors are 2.10 and 3.31, respectively. Our result provides a reliable CV laser source for advanced applications in optical imaging and optical manipulation.