【摘要】 谐波涡旋光束是一种典型的矢量光束,即产生的谐波信号具有螺旋型波前,在高容量光通信和非线性微纳光器件中有潜在应用前景.然而,目前的谐波涡旋光束产生器具有设计复杂,谐波转化效率低的局限性.本文提出并实验验证了基于准非线性自旋轨道耦合的高阶二次谐波涡旋光束,其拓扑荷数高达28阶,这是现有报道中的最高数值.结果表明金螺旋相位板的准轨道角动量(拓扑荷数q)可以传递到单层二硫化钨所产生的谐波信号上,其拓扑荷数为ln=2nq(n为谐波阶次).该工作为新型高质量谐波涡旋光束的产生及应用开辟了新的途径.更多还原

【Abstract】 A harmonic vortex beam is a typical vector beam with a helical wavefront at harmonic frequencies(e.g.,second and third harmonics). It provides an additional degree of freedom beyond spin-and orbitalangular momentum, which may greatly increase the capacity for communicating and encoding information. However, conventional harmonic vortex beam generators suffer from complex designs and a low nonlinear conversion efficiency. Here, we propose and experimentally demonstrate the generation of a large second-harmonic(SH) vortex beam with quasi-nonlinear spin–orbit interaction(SOI). Highquality SH vortex beams with large topological charges up to 28 are realized experimentally. This indicated that the quasi-angular-momentum of a plasmonic spiral phase plate at the excitation wavelength(topological charge, q) could be imprinted on the harmonic signals from the attached WS2 monolayer. The generated harmonic vortex beam has a topological charge of ln= 2 nq(n is the harmonic order). The results may open new avenues for generating harmonic optical vortices for optical communications and enables novel multi-functional hybrid metasurface devices to manipulate harmonic beams.更多还原