基于石墨烯太赫兹超表面的特殊波束动态调控

Graphene terahertz metasurfaces for dynamic manipulation of special beams

摘要:

现有的大多数特殊波束(聚焦波束、艾里光束等)超表面通常采用金属结构单元，通过改变单元结构的尺寸和旋转角度等方式进行单一的波前调控，但对动态调谐波前的特殊波束超表面的研究很少。本文突破传统结构的壁垒，利用石墨烯独特的电可调性，构造出利用石墨烯费米能级动态调控波前的特殊波束超表面，可在动态调控波前上实现更灵活的自由性，满足更多、更复杂的相位需求。通过调控石墨烯费米能级获得不同的相位分布，动态调控焦点的空间位置、聚焦开关与焦点个数之间的切换以及影响艾里光束的参数等。所提出的动态调控波前特殊波束超表面可为太赫兹在高分辨成像、聚焦可调平面透镜、光学显微操作、激光微加工、光学子弹成型等方面的应用提供参考。

Abstract:

Most existing special beams(focused beams, Airy beams, etc.) metasurfaces usually use metallic materials for a single wavefront modulation by changing the dimensions of the cell structure, the angle of rotation, etc. There are fewer researches on metasurfaces for special beams with dynamically tunable wavefronts. Therefore, breaking the barrier of traditional structures, special beam metasurfaces which utilize Fermi energy levels of graphene to dynamically modulate the wavefront are constructed. Stronger freedom in dynamically modulating the wavefront can be realized in order to achieve more and more complex phase requirements. Focusing metasurfaces with tunable wavefront and tunable Airy beam metasurfaces are designed, different phase distributions are obtained by tuning the Fermi energy levels of graphene. Utilizing the dynamic wavefront, the spatial position of the focal point, the switching of the focusing switch with the number of focal points, and the parameters affecting the Airy beam can be regulated.The proposed dynamic tunable wavefront special beam metasurfaces are helpful for terahertz applications in high-resolution imaging, focus-tunable planar lenses, optical micromanipulation, laser micromachining, and optical bullet molding.