The spin-orbit interaction of photons on the interface with the refractive-index inhomogeneity corresponds to the interplay between the spin degree of freedom of light and the extrinsic orbital angular momentum, which is a photonic version of the spin Hall effect. It leads to a perpendicular spin-dependent displacement of light, i.e., the so-called Imbert-Fedorov (IF) shifts. For many measurements of the spin Hall effect of light (SHEL), the displacement between two opposite spins is at the order of the wavelength of light, which cannot be distinguishable by human eyes. The quantum weak measurement technology therefore has been utilized, which desires a complex experimental setup and hence limits potential practical applications. A natural question arises: is there a system supporting an IF shift associated with the SHEL that is large enough to be distinguished by human eyes?

Fig 1. Spin-orbital angular momentum coupling of light on the birefringent symmetrical metal cladding planar waveguide and the polarization-dependent resonances.

The research report an experiment showing the submillimeter Imbert-Fedorov shift from the ultrastrong spin orbital angular momentum coupling, which is a photonic version of the spin Hall effect, by measuring the reflection of light from the surface of a birefringent symmetrical metal cladding planar waveguide. The light incidents at a near-normal incident angle and excites resonant ultrahigh-order modes inside the waveguide. A 0.16-mm displacement of separated reflected light spots corresponding to two polarization states is distinguishable by human eyes. In our experiment, we demonstrate the control of polarizations of light and the direct observation of the spin Hall effect of light, which opens an important avenue towards potential applications for optical sensing and quantum information processing, where the spin nature of photons exhibits key features.

Fig2. Experimental setup and intensity distributions of incident and reflected light.

Published the paper Direct Visualizing the Spin Hall Effect of Light via Ultrahigh-Order Modes on Physical Review Letters at 04th Feb. 2020 .

Paper Link：https://link.aps.org/doi/10.1103/PhysRevLett.124.053902

DOI: 10.1103/PhysRevLett.124.053902