Weak Measurements of Light Chirality with a Plasmonic Slit

Abstract

We examine, both experimentally and theoretically, an interaction of tightly focused polarized light with a slit on a metal surface supporting plasmon-polariton modes. Remarkably, this simple system can be highly sensitive to the polarization of the incident light and offers a perfect quantum weak measurement tool with a built-in postselection in the plasmon-polariton mode. We observe the plasmonic spin Hall effect in both coordinate and momentum spaces which is interpreted as weak measurements of the helicity of light with real and imaginary weak values determined by the input polarization. Our experiment combines the advantages of (i) quantum weak measurements, (ii) near-field plasmonic systems, and (iii) high-numerical aperture microscopy in employing the spin-orbit interaction of light and probing light chirality.

Extraordinary momentum and spin in evanescent waves

“…This induces a rotation of the fields in the propagation (x,z) plane (see Fig. 2a,d), and generates the spin s y / Im E Ã z E x þ H Ã z H x À Á independently of s. Recently, we described such spin for surface plasmon-polaritons 42 , and it was shown that the imaginary longitudinal field component plays an important role in optical coupling processes 44,45 . The second feature is the inhomogeneous intensity wpexp( À 2kx).…”

Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes

“…In particular, we have shown that the new effect of near-field interference enables the broadband mapping of light in space, depending on its polarization handedness. This mapping is similar to the spin Hall effect, which has recently been considered also in optical domain for new quantum optical applications 7,8,10,11 employing the structured interfaces to break the inversion symmetry. In our realization, this effect is observed due to the inversion symmetry broken by the radiating dipole.…”

“…The approach based on discrete nanoresonators and their arrangements in various kinds of metamaterials has already resulted in many applications, such as cloaking 3 and perfect lensing 4 , as well as spontaneous emission and nonlinearity engineering 5 . The direction of light propagation can also be controlled by the polarization degree of freedom [6][7][8][9][10][11][12] . In particular, when circularly polarized light interacts with specifically designed nanostructured metasurfaces that break spatial inversion symmetry, photons of different polarizations (optical spin) may take different trajectories, in close analogy to the spin Hall effect for electrons [7][8][9][10][11] .…”

“…The direction of light propagation can also be controlled by the polarization degree of freedom [6][7][8][9][10][11][12] . In particular, when circularly polarized light interacts with specifically designed nanostructured metasurfaces that break spatial inversion symmetry, photons of different polarizations (optical spin) may take different trajectories, in close analogy to the spin Hall effect for electrons [7][8][9][10][11] . In terms of manipulation of emission properties, anisotropic metamaterials with hyperbolic isofrequency surfaces have been proposed for nonresonant enhancement of the spontaneous emission rate 13 , which are fundamentally limited only by the basic dimensionality of an artificial unit cell 14 and nonlocal effects 15 .…”

Spin-dependent optics with metasurfaces

“…Actually, such a spin-orbit coupling can also occur even for a scatterer with other shapes in scattering the incident light to surface plasmon. Figure 8A shows an example of a single slit illuminated by a tightly focused linearly or elliptically polarized light beam [96]. The shift in either the focal point or the direction of the generated surface waves is measured using a "weak measurement" approach.…”