A study of the rotational spin-Hall effect in higher order Gaussian beams

Spin-to-orbit conversion of light is a dynamical optical phenomenon in a non-paraxial fields, which plays an important role in various manifestations of the optical Hall Effect. Here, we demonstrate – both theoretically and experimentally – the rotational Hall Effect for a higher order Gaussian beam (HG10 ) in an optical tweezers configuration. Our theoretical results clearly reveal that for an input spin polarized HG10 mode (right/left circularly polarized), the orthogonal circularly polarized component (left/ right), generated due to angular momentum conservation following spin-orbit interaction, displays a large rotation of the intensity profile – a clear signature of the rotational Hall effect. We demonstrate the same experimentally, although the impossibility of separating out the longitudinal component from the detected intensity profile prevents us from obtaining rotation values as large as the theoretical predictions. We also measure the rotational shift as a function of the refractive index contrast in the beam path of the optical tweezers, and observe a proportional increase in general. We envisage interesting applications in inducing complex dynamics in optically trapped birefringent particles due to the spin-orbit conversion in our system.