Optical nanoprobing via spin-orbit interaction of light

Abstract

We show, both theoretically and experimentally, that high-numerical-aperture (NA) optical microscopy is accompanied by strong spin-orbit interaction of light, which translates fine infomation about the specimen to the polarization degrees of freedom of light. An 80nm gold nano-particle scattering the light in the focus of a high-NA objective generates angular momentum conversion which is seen as a non-uniform polarization distribution at the exit pupil. We demonstrate remarkable sensitivity of the effect to the position of the nano-particle: Its subwavelength displacement produces the giant spin-Hall effect, i.e., macro-separation of spins in the outgoing light. This brings forth a far-field optical nanoprobing technique based on the spin-orbit interaction of light.