Mazanov Maxim, Sugic Danica, Alonso Miguel A, Nori Franco, Bliokh Konstantin Y
V. N. Karazin Kharkiv National University, Kharkiv, 61022, Ukraine.
Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wako-shi, Saitama 351-0198, Japan.
Nanophotonics. 2021 Aug 23;11(4):737-744. doi: 10.1515/nanoph-2021-0294. eCollection 2022 Jan.
Transverse (Hall-effect) and Goos-Hänchen shifts of light beams reflected/refracted at planar interfaces are important wave phenomena, which can be significantly modified and enhanced by the presence of intrinsic orbital angular momentum (OAM) in the beam. Recently, optical spatiotemporal vortex pulses (STVPs) carrying a purely transverse intrinsic OAM were predicted theoretically and generated experimentally. Here we consider the reflection and refraction of such pulses at a planar isotropic interface. We find theoretically and confirm numerically novel types of OAM-dependent transverse and longitudinal pulse shifts. Remarkably, the longitudinal shifts can be regarded as time delays, which appear, in contrast to the well-known Wigner time delay, without temporal dispersion of the reflection/refraction coefficients. Such time delays allow one to realize OAM-controlled slow (subluminal) and fast (superluminal) pulse propagation without medium dispersion. These results can have important implications in various problems involving scattering of localized vortex states carrying transverse OAM.
光束在平面界面反射/折射时的横向（霍尔效应）和古斯-汉欣位移是重要的波动现象，光束中固有轨道角动量（OAM）的存在会对其产生显著的改变和增强。最近，理论上预测并通过实验产生了携带纯横向固有OAM的光学时空涡旋脉冲（STVP）。在此，我们考虑此类脉冲在平面各向同性界面处的反射和折射。我们通过理论推导并数值验证了新型的依赖于OAM的横向和纵向脉冲位移。值得注意的是，纵向位移可被视为时间延迟，与著名的维格纳时间延迟不同，这种时间延迟在反射/折射系数无时间色散的情况下出现。这种时间延迟使得人们能够在无介质色散的情况下实现OAM控制的慢（亚光速）和快（超光速）脉冲传播。这些结果在涉及携带横向OAM的局域涡旋态散射的各种问题中可能具有重要意义。
