对两束平行、离轴厄米-高斯(H-G)涡旋光束在束腰面形成的合成光涡旋(OV)及其演化特性做了研究。结果表明, 合成光涡旋的数目、位置和净拓扑电荷不仅与控制参数, 包括相对相位、振幅比、束腰宽度比和离轴参数有关, 也与H-G涡旋光束的模式结构有关。适当改变控制参数和模式以及在自由空间演化中, 会出现合成光涡旋的移动、产生和湮灭,并且拓扑电荷不总是守恒的。特别是, 对TEM00和TEM01模涡旋光束形成的合成光涡旋, 当改变相对相位时拓扑电荷也不守恒。所得结果对合成光涡旋的控制和应用是有用的。

The composite optical vortices (OVs) formed by two parallel, off-axis Hermite-Gaussian (H-G) vortex beams at the waist plane and their evolution behavior are studied. It is shown that the number, position and net topological charge of composite OVs depend not only on the control parameter, including the relative phase, amplitude ratio, waist width ratio and off-axis distance, but also on the mode structure of H-G vortex beams. By appropriately varying the control parameter and mode of H-G vortex beams and in the free-space evolution, the motion, creation and annihilation of composite vortices may appear, and the topological charge does not always remain unchanged. In particular, for the composite OVs formed by TEM00 and TEM01 vortex beams, the topological charge is not conserved by changing relative phase. The results are useful for the composite OV control and applications.