Kim Minkyung, Lee Dasol, Kim Yeseul, Rho Junsuk
Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
School of Mechanical Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
Nanophotonics. 2022 Sep 20;11(20):4591-4600. doi: 10.1515/nanoph-2022-0447. eCollection 2022 Sep.
The spin Hall effect of light, i.e., the microscopic and spin-dependent transverse splitting of linearly polarized light into circular polarizations at an optical interface, has been considered as a promising candidate for high-precision measurement when combined with a weak measurement technique. However, in those previous demonstrations, the precision is determined by the interface of interest, hindering its versatility. Here, by leveraging the direct correlation of precision with the spin Hall shift, we propose nanophotonic-assisted approaches to increase the precision of the weak measurement by controlling the spin Hall effect of light at the target interface. The refractive index sensing of an isotropic medium is demonstrated as a proof of concept, in which the precision can be increased, in principle, to infinity by placing an index-below-unity slab in the vicinity of the target interface. Furthermore, a single-layer metasurface comprising two-dimensional subwavelength patterns is introduced as an experimentally favorable platform. This study lays the foundation for nondestructive and high-precision investigation of unknown parameters of interfaces and will find wide sensing applications in material science, medical engineering, and other interdisciplinary fields.
光的自旋霍尔效应，即线偏振光在光学界面处发生的微观且依赖于自旋的横向分裂为圆偏振光的现象，当与弱测量技术相结合时，被认为是高精度测量的一个有前景的候选方案。然而，在之前的那些演示中，精度由感兴趣的界面决定，这限制了其通用性。在此，通过利用精度与自旋霍尔位移的直接相关性，我们提出了纳米光子辅助方法，通过控制目标界面处光的自旋霍尔效应来提高弱测量的精度。作为概念验证，展示了对各向同性介质的折射率传感，其中通过在目标界面附近放置折射率低于1的平板，原则上精度可以提高到无穷大。此外，引入了一种由二维亚波长图案组成的单层超表面作为实验上有利的平台。这项研究为无损且高精度地研究界面未知参数奠定了基础，并将在材料科学、医学工程和其他跨学科领域中找到广泛的传感应用。
