锥角调制的圆艾里涡旋光束构建光学针

Optical needle constructed by conical-angle modulated circular Airy vortex beams

光学针是一种特殊的空间光场分布,具有极小的横向光斑尺寸,可以突破衍射极限,同时在纵向上拥有较长的焦深.光学针通常利用透镜对光束进行紧聚焦来产生,本文利用圆艾里光束固有的自聚焦特性来构建光学针.研究结果表明,锥角调制的圆偏振圆艾里涡旋光束在选取合适的拓扑荷后,可以产生光学针.这是因为在锥角调制下,光束的纵向分量被显著增强,而纵向分量光场具有极小的横向光斑尺寸.光学针的焦深与光束的主环半径近似呈线性关系,因此增大主环半径可以有效增强光学针的焦深.此外,具有不同拓扑荷的圆艾里涡旋光束可以构建出不同结构的空间光场.本文的研究有望在超分辨成像和光学微操控等领域具有潜在应用价值.

An optical needle is a specialized spatial light field characterized by an extremely small transverse spot size,capable of breaking through the diffraction limit,and also prossessing a long focal depth in the longitudinal direction.Typically,optical needles are generated by tightly focusing a beam using a lens.In this work,the generation of optical needles is demonstrated by using circular Airy vortex beams(CAVBs)through adjusting the conical angle.The CAVBs have a uniform distribution of circular polarization,thus eliminating the need for radial polarization states.Our research indicates that under the conical angle modulation,CAVBs with a topological charge of–1(left-handed circular polarization)and 1(right-handed circular polarization)can form optical needles.These optical needles possess a minimal transverse spot size,enabling them to exceed the diffraction limit while maintaining a long depth of focus.Furthermore,the depth of focus of the optical needle is almost linearly related to the primary ring radius of the beam.Increasing the primary ring radius can effectively enhance the depth of focus.CAVBs with different topological charges generate distinct hollow light fields,unlike optical needles.This is because the longitudinal component of the light beam is significantly enhanced by adjusting the conical angle.Only CAVBs with the appropriate topological charge exhibit a longitudinal light field near the optical axis,leading to the formation of optical needles.In contrast,other charges result in a hollow longitudinal light field,creating different hollow light fields.These research findings could have significant applications in super-resolution imaging and optical micromanipulation.