Opt Lett. 2018 Jun 15;43(12):2823-2826. doi: 10.1364/OL.43.002823.
Upon reflection, a light beam embedded with m-order orbital angular momentum (OAM) will undergo the Imbert-Fedorov (IF) shift, which induces OAM sidebands. The energies of the neighboring {-m-1} and {-m+1} sideband modes of the reflected beam are always equal. Controllable OAM sidebands are theoretically achieved by introducing a monolayer graphene in a three-layer structure composed of air, hexagonal boron nitride, and metal. By modulating the Fermi energy of graphene, the OAM-dependent IF shift can be tuned from positive to negative values, and the OAM sideband modes can be suppressed or enhanced, since the reflectivity for perpendicular and parallel polarizations vary with the Fermi energy. These findings provide an alternative method for the control of optical OAM in the terahertz region.
经反思，嵌入 m 阶轨道角动量（OAM）的光束将经历 Imbert-Fedorov（IF）位移，从而产生 OAM 边带。反射光束的相邻{-m-1}和{-m+1}边带模式的能量始终相等。通过在由空气、六方氮化硼和金属组成的三层结构中引入单层石墨烯，理论上可以实现可控的 OAM 边带。通过调节石墨烯的费米能，可以将 OAM 相关的 IF 位移从正值调至负值，并且可以抑制或增强 OAM 边带模式，因为垂直和平行偏振的反射率随费米能而变化。这些发现为太赫兹区域光 OAM 的控制提供了一种替代方法。
