Unidirectional ring vortex laser using a wedge-plate shearing interferometer.

In response to growing demand from optical vortex (OV) beam applications, numerous generation techniques have been developed competing in power scalability, purity, and wavelength flexibility. Direct vortex emission from lasers typically grants access to efficient, high power, and pure mode generation. In this work we demonstrate a compact, unidirectional Nd:YVO ring laser with an intracavity wedge-plate shearing interferometer (WPSI) as an output coupler, which converted the internal Gaussian mode to LG (Laguerre-Gaussian OV) output. It directly generated a watt-level LG OV with high mode purity (98%) in a single longitudinal mode. The monolithic WPSI has advantages in stability and simplicity compared to other designs. The system is compact and cheap, using off-the-shelf components, and can be readily adapted to any gain media, widening the scope for OV generation at wavelengths currently unobtainable using competing methods.