Free-space realization of tunable pin-like optical vortex beams

We demonstrate, both analytically and experimentally, free-space pin-like optical vortex beams (POVBs).Such angular-momentum-carrying feature tunable peak intensity undergo robust anti-diffracting propagation, realized by judiciously modulating the amplitude phase profile of a standard laser beam. Specifically, they are generated superimposing radially-symmetric power-law on helical structure, which allows inclusion an orbital angular momentum term to POVBs. During propagation in free-space, these POVBs initially exhibit autofocusing dynamics, subsequently, their patterns morph into high-order Bessel-like characterized hollow-core annular main-lobe with constant or width during propagation. In contrast numerous previous endeavors Bessel beams, our work represents first demonstration long-distance generation 'pins', evolution controlled impressed structure. Both Poynting vectors radiation forces associated also numerically analyzed, revealing novel properties that may be useful for wide range applications.