对称艾里涡旋光束的传播特性

Propagation Characteristic of Symmetric Airy Vortex Beams

提出了一种对称艾里涡旋光束.在对称立方相位的基础上引入螺旋相位因子形成新的相位图,加载该相位的高斯光束经傅里叶变换后产生对称艾里涡旋光束.研究表明:对称艾里涡旋光束出现自聚焦现象,且由于轴上涡旋的存在,其中心呈现中空现象,涡旋结构携带的轨道角动量使光束在初始平面处发生旋转,拓扑荷数越大,中空结构越大,旋转角度也越大,而拓扑荷数的正负仅改变光束的旋向.理论分析表明,离轴涡旋在初始平面处,因与光轴中心距离较远,并不会影响对称艾里光束主瓣的能量,即中心并无光强为零区域,但随着传播距离的增加,离轴涡旋逐渐出现在对称艾里光束其中的一个主瓣上.此外,对称艾里光束还可以加载多个离轴涡旋,能同时无损伤地捕获多个微粒.该光束不仅具有自聚焦特性,并且其中心呈中空结构,同时还携带轨道角动量,在光学微操纵与生物医学等方面有潜在应用.

A symmetric Airy vortex beam can be generated by modulating a Gaussian beam imposed on an improved phase pattern, where helical phase factor is introduced in symmetric cubic phase. The experimental results and numerical simulations demonstrate that such beams possess autofocusing characteristic and have a dark core owing to on-axis vortex. Such a special structure causes the beams to rotate in the initial plane. The lager topological charge, the bigger dark area, the greater rotating angle. The positive or negative topological charge only changes the rotating direction. Theoretical analysis shows that in the initial plane, the main lobe of symmetric Airy beams and off-axis vortex have nearly no influence. However, off-axis vortex will gradually appear on one of the main lobes of the symmetric Airy beams during propagation. In addition, the symmetric Airy beams also can embed multiple off-axis vortices which can capture multiple particles without damage. Due to the above characteristics, the beams have potential applications in optical trapping and biomedicine.