自由空间可调谐类针状光学涡旋光束的实现
Free-space Realization of Tunable Pin-like Optical Vortex Beams
摘要：
通过理论分析和实验研究，证明了自由空间类钉光学涡旋光束（POVBs）具有峰值强度可调的特点，并通过对标准光束的振幅和相位进行适当的调制，实现了稳健的抗衍射传输.具体地说，它们是通过在螺旋相位结构上叠加径向对称幂律相位而产生的，这允许将轨道角动量项包含在POVB中。在自由空间中的传播过程中，这些POVB最初表现出自聚焦动力学，随后，它们的振幅图案变形成高阶贝塞尔样的轮廓，其特征在于在传播过程中具有恒定或可调宽度的中空芯和环形主瓣。与许多以前的努力贝塞尔光束相比，我们的工作代表了第一次演示的长距离自由空间产生的光学涡旋“针”，其峰值强度的演变控制的印象振幅结构。与这些光束相关的坡印廷矢量和光辐射力也进行了数值分析，揭示了新的属性，可能是有用的广泛的应用。
英文摘要：
We demonstrate, both analytically and experimentally, free-space pin-like optical vortex beams (POVBs).Such angular-momentum-carrying beams feature tunable peak intensity and undergo robust anti-diffracting propagation, realized by judiciously modulating both the amplitude and the phase profile of a standard laser beam. Specifically, they are generated by superimposing a radially-symmetric power-law phase on a helical phase structure, which allows the inclusion of an orbital angular momentum term to the POVBs. During propagation in free-space, these POVBs initially exhibit autofocusing dynamics, and subsequently, their amplitude patterns morph into a high-order Bessel-like profile characterized by a hollow-core and an annular main-lobe with a constant or tunable width during propagation. In contrast with numerous previous endeavors on Bessel beams, our work represents the first demonstration of long-distance free-space generation of optical vortex 'pins', with their peak intensity evolution controlled by the impressed amplitude structure. Both the Poynting vectors and the optical radiation forces associated with these beams are also numerically analyzed, revealing novel properties that may be useful for a wide range of applications.
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