The spin Hall effect of light (SHEL), the transverse splitting of light into two circularly polarized components via refraction or reflection, offers high-precision, nondestructive inspection of unknown interfaces when combined with a signal amplification technique called weak measurement. However, its application in detecting dynamics is limited due to its multistep process. Here, we condense the procedure into a single step, enabling calibration-free, single-shot measurement of the SHEL by replacing one component of the conventional setup with a polarization beamsplitting metasurface. Our approach allows for instantaneous evaluation of the SHEL, even with fluctuations in the original beam position. As proof of concept, we apply metasurface-assisted weak measurements to both static and dynamic scenarios, where the experimental results obtained from a single captured image demonstrate nice agreement with theory. This real-time observation of the SHEL highlights its potential for high-precision monitoring of dynamic processes such as biomedical sensing and chemical analysis.

Spin-orbit coupling, a fundamental mechanism underlying topological insulators, has been introduced to construct the latter's photonic analogs, or photonic topological insulators (PTIs). However, the intrinsic lack of electronic spin in photonic systems leads to various imperfections in emulating the behaviors of topological insulators. For example, in the recently demonstrated three-dimensional (3D) PTI, the topological surface states emerge, not on the surface of a single crystal as in a 3D topological insulator, but along an internal domain wall between two PTIs. Here, by fully abolishing spin-orbit coupling, we design and demonstrate a 3D PTI whose topological surface states are self-guided on its surface, without extra confinement by another PTI or any other cladding. The topological phase follows the original Fu's model for the topological crystalline insulator without spin-orbit coupling. Unlike conventional linear Dirac cones, a unique quadratic dispersion of topological surface states is directly observed with microwave measurement. Our work opens routes to the topological manipulation of photons at the outer surface of photonic bandgap materials.

Abstract The spin Hall effect of light (SHEL) is the microscopic splitting of light into two circular polarizations at the optical interface along the perpendicular direction. With the advent of metamaterials/metasurfaces and their fast‐developing applications, the SHEL has been garnering significant scientific interest. Here, the principle and recent developments in SHEL research is reviewed. A theoretical description of the SHEL is provided, including the formalism and general techniques. Also, recent studies on and applications of the SHEL are extensively reviewed, including the enhancement of the spin Hall shift and efficiency, implementation of dynamic tunability, elimination of polarization dependence, and precision measurements. The review is concluded with a discussion on the future direction and prospects of the SHEL.

The spin Hall effect of light refers to a spin-dependent transverse splitting of light at a planar interface. Previous demonstrations to enhance the splitting have suffered from exceedingly low efficiency. Achievements of the large splitting with high efficiency have been reported in the microwave, but those in the optical regime remain elusive. Here, an approach to attain the large splitting with high efficiency in the near-infrared is proposed and experimentally demonstrated at 800 nm by using a dielectric metasurface. Modulation of the complex transmission of the metasurface leads to the shifts that reach 10λ along with efficiencies over 70% under two linear polarizations. Our work extends the recent attempts to achieve the large and efficient spin Hall effect of light, which have been limited only to the microwave, to the optical regime.

The spin Hall effect of light (SHEL), the transverse splitting of light into two circularly polarized components via refraction or reflection, offers high-precision, nondestructive inspection of unknown interfaces when combined with a signal amplification technique called weak measurement. However, its application in detecting dynamics is limited due to its multistep process. Here, we condense the procedure into a single step, enabling calibration-free, single-shot measurement of the SHEL by replacing one component of the conventional setup with a polarization beamsplitting metasurface. Our approach allows for instantaneous evaluation of the SHEL, even with fluctuations in the original beam position. As proof of concept, we apply metasurface-assisted weak measurements to both static and dynamic scenarios, where the experimental results obtained from a single captured image demonstrate nice agreement with theory. This real-time observation of the SHEL highlights its potential for high-precision monitoring of dynamic processes such as biomedical sensing and chemical analysis.

Spin-orbit coupling, a fundamental mechanism underlying topological insulators, has been introduced to construct the latter's photonic analogs, or photonic topological insulators (PTIs). However, the intrinsic lack of electronic spin in photonic systems leads to various imperfections in emulating the behaviors of topological insulators. For example, in the recently demonstrated three-dimensional (3D) PTI, the topological surface states emerge, not on the surface of a single crystal as in a 3D topological insulator, but along an internal domain wall between two PTIs. Here, by fully abolishing spin-orbit coupling, we design and demonstrate a 3D PTI whose topological surface states are self-guided on its surface, without extra confinement by another PTI or any other cladding. The topological phase follows the original Fu's model for the topological crystalline insulator without spin-orbit coupling. Unlike conventional linear Dirac cones, a unique quadratic dispersion of topological surface states is directly observed with microwave measurement. Our work opens routes to the topological manipulation of photons at the outer surface of photonic bandgap materials.

Abstract The spin Hall effect of light (SHEL) is the microscopic splitting of light into two circular polarizations at the optical interface along the perpendicular direction. With the advent of metamaterials/metasurfaces and their fast‐developing applications, the SHEL has been garnering significant scientific interest. Here, the principle and recent developments in SHEL research is reviewed. A theoretical description of the SHEL is provided, including the formalism and general techniques. Also, recent studies on and applications of the SHEL are extensively reviewed, including the enhancement of the spin Hall shift and efficiency, implementation of dynamic tunability, elimination of polarization dependence, and precision measurements. The review is concluded with a discussion on the future direction and prospects of the SHEL.

The spin Hall effect of light refers to a spin-dependent transverse splitting of light at a planar interface. Previous demonstrations to enhance the splitting have suffered from exceedingly low efficiency. Achievements of the large splitting with high efficiency have been reported in the microwave, but those in the optical regime remain elusive. Here, an approach to attain the large splitting with high efficiency in the near-infrared is proposed and experimentally demonstrated at 800 nm by using a dielectric metasurface. Modulation of the complex transmission of the metasurface leads to the shifts that reach 10λ along with efficiencies over 70% under two linear polarizations. Our work extends the recent attempts to achieve the large and efficient spin Hall effect of light, which have been limited only to the microwave, to the optical regime.

Abstract The spin Hall effect of light (SHEL), a spin‐dependent transverse splitting of light at an optical interface, is intrinsically an incident‐polarization‐sensitive phenomenon. Recently, an approach to eliminate the polarization dependence by equalizing the reflection coefficients of two linear polarizations has been proposed, but is only valid when the beam waist is sufficiently larger than the wavelength. Here, it is demonstrated that an interface, at which the reflection coefficients of the two linear polarizations are the same and so are their derivatives with respect to the incident angle, supports the polarization‐independent spin Hall shift, even when the beam waist is comparable to the wavelength. In addition, an isotropic–anisotropic interface that exhibits the polarization‐independent spin Hall shift over the entire range of incident angles is presented. Monte‐Carlo simulations prove that spin Hall shifts are degenerate under any polarization and reach a half of beam waist under unpolarized incidence. An application of the beam‐waist‐scale SHEL as a tunable beam‐splitting device that is responsive to the incident polarization is suggested. The spin Hall shift that is independent of the incident polarization at any incident angle will facilitate a wide range of applications including practical spin‐dependent devices and active beam splitters.

Radiative cooling (RC) is a sustainable technology that passively lowers the temperature of terrestrial objects through thermal radiation, dissipating heat into outer space via the atmospheric window, unlike conventional cooling systems that require electricity and release waste heat to the environment. In recent years, RC technologies have advanced rapidly, moving steadily toward practical implementation and commercialization. Here, this mega-review offers a comprehensive overview of RC, encompassing its fundamental background, the underlying photonic and thermal principles, and fabrication approaches for constructing efficient cooling devices. We discuss a variety of RC structures along with their design strategies and explore the diverse functionalities that adapt RC toward particular requirements. We further review emerging applications of RC, highlighting practical implementations. Finally, we outline the key challenges and future directions, offering perspectives and insights to guide continued progress in this rapidly advancing field.

Abstract Transparent radiative cooling enables passive thermal management by selectively reflecting solar radiation and emitting thermal energy, thereby offering a promising solution for energy‐efficient cooling in transparent applications. Despite recent progress in the development of transparent radiative coolers, achieving a balance between high visible transparency and effective solar reflection remains a critical challenge in enhancing the cooling performance. In this study, a transparent radiative cooler comprising a 50 µm‐thick polydimethylsiloxane (PDMS) emitter integrated with a sophisticated metal‐dielectric multilayer is evaluated both experimentally and theoretically. The theoretical simulations demonstrate a visible transmittance >82% and a near‐infrared reflectance >92%, with a sharp transition between spectral regimes. Experimental characterizations confirm a visible transmittance of 48% alongside an enhanced near‐infrared reflectance of 98%, thereby validating robust cooling performance under real‐world conditions. Additionally, daytime outdoor measurements indicate that the cooler achieves a maximum temperature reduction of 10.8 °C compared to conventional PDMS‐coated glass. Furthermore, global simulations illustrate the cooling effect of this cooler under diverse climatic conditions, highlighting its potential for use in various terrestrial areas.