Shim Sangmin, Yu Kyung-Hyun, Kim Minkyung, Lee Dasol
Department of Biomedical Engineering, Yonsei University, Wonju, 26493, Republic of Korea.
School of Mechanical and Robotics Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea.
Sci Rep. 2025 Jul 21;15(1):26507. doi: 10.1038/s41598-025-12349-0.
The spin Hall effect of light, a transverse and spin-dependent splitting at an optical interface, generally depends on the interface properties. By contrast, the spin Hall effect of circularly polarized light is interface-independent, which aids precise nanoscale displacement control. However, the spin Hall-shifted beam generally exhibits low efficiency near normal incidence, where the shift is large. The static nature of metasurfaces with in-plane anisotropy that have been proposed to address this limitation renders them unsuitable for dynamic or reconfigurable applications. In this study, we numerically demonstrated an electrically tunable metasurface that enabled binary-state switching between spin-Hall-shifted and suppressed reflection efficiencies. The metasurface comprised a grating structure and an indium tin oxide layer, whose permittivity was dynamically modulated via an electrical bias, resulting in changes in the reflection amplitude and phase, and thus, in the spin Hall efficiency. Without an applied voltage, the metasurface exhibited suppressed reflection in the spin-Hall-shifted component. By contrast, the dominance switched to spin Hall-shifted reflection upon voltage application. This approach enables the selective control of the spin-dependent reflection intensity without altering the beam displacement, thereby facilitating reconfigurable spin-optical photonic systems.
光的自旋霍尔效应，即光学界面处的横向和自旋相关分裂，通常取决于界面特性。相比之下，圆偏振光的自旋霍尔效应与界面无关，这有助于精确的纳米级位移控制。然而，自旋霍尔位移光束在垂直入射附近通常表现出低效率，此时位移较大。为解决这一限制而提出的具有面内各向异性的超表面的静态特性使其不适用于动态或可重构应用。在本研究中，我们通过数值方法证明了一种电可调超表面，它能够在自旋霍尔位移和抑制反射效率之间进行二态切换。该超表面由一个光栅结构和一个氧化铟锡层组成，其介电常数通过电偏置进行动态调制，从而导致反射幅度和相位发生变化，进而使自旋霍尔效率发生改变。在没有施加电压时，超表面在自旋霍尔位移分量中表现出抑制反射。相比之下，施加电压后，主导地位切换到自旋霍尔位移反射。这种方法能够在不改变光束位移的情况下选择性地控制自旋相关反射强度，从而促进可重构自旋光光子系统的发展。
