Experimental study on obtaining visible hollow light of 532nm based on conical refraction of biaxial crystal

At present, the research on hollow light mostly focuses on the near-infrared invisible light band, however, with the development of space light field and nonlinear optics, the nonlinear frequency conversion process of hollow light is also paid attention to, but most of them are focused on the theoretical level of frequency transformation, and few hollow light frequency conversion with realizability and applicability is available. In this paper, the visible hollow light conversion from 1064 nm to 532 nm is realized by using the conical refraction of biaxial crystal and a novel technical scheme based on the plane concave cavity structure and combining with nonlinear frequency conversion. The gain medium Nd:YVO4 is pumped by 808 nm LD, and LBO I phase matching is used for intra-cavity frequency doubling. When the pump power is 10.49W, 532nm hollow light output is 0.067W; finally, when the pump power is 23.09W, the maximum output power of 532nm hollow light is 1.146W, and the maximum light-to-light conversion efficiency of 1064nm-532nm is 27.4%. During the experiment, the cone refraction led to the formation of the 532nm hollow spot was observed, and the output performance of the 532nm hollow light was analyzed. The experimental scheme in this paper has the advantages of simple structure, low maladjustment sensitivity and high mechanical stability, which is conducive to frequency conversion in resonant cavity. It provides a novel and effective technical means for obtaining hollow light in visible light band, and broadens the application of hollow light in quantum computing and communication.