Direct Visualizing the Spin Hall Effect of Light via Ultrahigh-Order Modes

The spin Hall effect of light (SHEL), which refers to a spin-dependent and transverse splitting of refraction and reflection phenomena, inherently depends on the polarization states of incidence. Most previous research has focused on horizontally or vertically polarized incidence, in which the analytic expressions of the shift are well-formulated and the SHEL appears symmetrically in both shift and intensity. However, the SHEL under arbitrarily polarized or unpolarized incidence has remained largely unexplored. Here, it is proved analytically and numerically that the SHEL is independent of the incident polarization and is symmetrical in shift if the two linear polarization states have the same Fresnel coefficients. Moreover, under an unpolarized incidence composed of a large number of completely random polarization states, the reflected beam is split in half into two circularly polarized components that undergo the same amount of splitting but in opposite directions. This result demonstrates that under unpolarized incidence, the SHEL occurs exactly as it does under horizontally or vertically polarized incidence. It is believed that the incident-polarization-independent SHEL can broaden the applicability of the SHEL to cover optical systems in which the polarization is unspecified.

Section: Introductionmentioning

confidence: 99%

Spin Hall Effect under Arbitrarily Polarized or Unpolarized Light

Kim

Lee

Rho

2021

“…Our reinterpretations suggest that previous spin-Hall shifts obtained with LP incidences might not be fundamental quantities, and re-examining them under the CP bases could yield new insights, especially in the cases where Fresnel's coefficients exhibit singular behaviors. [27][28][29][30][31][32] For example, the spin-Hall shifts of reflected beam at incidence near Brewster angle is abnormally enhanced under LP incidences, while its mechanism remains obscure. [27][28][29] Employing our analyses using CP bases, we find that the reflected light beam exhibits a severely deformed pattern caused by the destructive interference between normal and abnormal modes, because of r +− (K i ) = −r ++ (K i ) at the Brewster angle.…”

Section: Reinterpreting Results Computed By Previous Theoriesmentioning

confidence: 99%

Topology‐Induced Phase Transitions in Spin‐Orbit Photonics

Ling

Guan

Cai

et al. 2021

Spin‐controlled vortex generation and spin‐Hall effect, two distinct effects discovered in optics, have been extensively studied recently. However, while physical origins of two effects are both due to spin‐orbit interactions, their inherent connections remain obscure which also hinders further explorations on the manipulations of them. Here, in studying the scattering of a spin‐polarized light beam at sharp interfaces, an intriguing phase transition between vortex generation and spin‐Hall shift trigged by varying the incidence angle is revealed. After reflection/refraction, the beam contains two components: normal and abnormal modes acquiring spin‐redirection‐Berry phases and Pancharatnam–Berry phases, respectively. Inside the abnormal beam, two classes of wave components gain Pancharatnam–Berry phases with distinct topological natures, generating intrinsic and extrinsic orbital angular momenta (OAM), respectively. Enlarging incidence angle changes the relative portions of these two contributions, making the abnormal beam undergo a phase transition from vortex generation to spin‐Hall shift. Such intriguing effect is experimentally observed at a purposely designed metamaterial slab, exhibiting efficiency enhanced by several‐thousand times compared to that at a conventional slab. These findings unify two previously discovered effects in a single framework, reinterpret previous results with clearer pictures, and shed light on understanding other physical effects involving the competition between intrinsic and extrinsic OAM.

“…The analytical formulas shown in Equations () and () have been used to evaluate the SHEL in many literature. [ 26–28,34,52 ] However, it is an indirect method to calculate the SHEL from transmission or reflection spectra. To confirm the spin‐dependent splitting directly and visually, we perform an additional measurement to obtain a spatial profile of the Stokes parameters

S = (S_{0}, S_{1}, S_{2}, S_{3})

, which represent polarization states of a beam, [ 53 ] along the splitting direction.…”

Section: Resultsmentioning

confidence: 99%

“…A goal that naturally comes up next in SHEL community is to increase the amount of shift by up to an order of wavelength and even beyond. Attempts to increase the SHEL have included exploiting specialized materials such as metal‐dielectric multilayers, [ 26–29 ] dielectric grating on a metallic layer, [ 30 ] epsilon‐near‐zero materials, [ 31,32 ] and a metasurface [ 33 ] or using specific circumstances such as resonant ultrahigh‐order modes, [ 34 ] surface plasmon resonances, [ 35 ] bound states in the continuum, [ 32 ] and reflections near the Brewster angle (

θ_{B}

). [ 36–39 ] The enhanced SHEL, including a few hundreds of micrometer scale shift that is even distinguishable by human eyes, [ 34 ] has shown a potential in practical applications such as helicity‐dependent switches and sensors.…”

Section: Introductionmentioning

confidence: 99%

Spin Hall Effect of Light with Near‐Unity Efficiency in the Microwave

Kim

Lee

Cho

et al. 2020

The spin Hall effect of light (SHEL) refers to a transverse and spin‐dependent shift of light in real space at an optical interface. Previous studies of enhancing the SHEL have involved extremely low efficiency, and achieving a large SHEL and high efficiency simultaneously has never been reported. Here, an approach using anisotropic impedance mismatching to attain a large SHEL with near‐unity efficiency in the microwave spectrum is proposed. A wire medium that has a near‐unity transmission for one polarization and low transmission for the other is used to achieve high efficiency. The spin‐dependent splitting is experimentally confirmed by measuring transmission coefficients and the spatial profile of Stokes parameters. The large SHEL with near‐unity efficiency will enable highly efficient devices with spin‐selective functionalities.