Controlling photonic spin Hall effect via exceptional points

TL;DR

This paper demonstrates how to control and enhance the photonic spin Hall effect by exploiting exceptional points in PT-symmetric systems, revealing a method to modulate spin-dependent beam shifts with high sensitivity.

Contribution

It introduces a novel approach to modulate the photonic SHE using exceptional points, linking phase jumps at these points to transverse shift control in PT-symmetric systems.

Findings

Transverse shift is zero at exceptional points but enhanced nearby.

The transverse shift switches sign across the exceptional point.

Photonic SHE can be used to precisely locate exceptional points.

Abstract

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of an impinging optical beam driven by its polarization handedness, has many applications including precise metrology and spin-based nanophotonic devices. It is highly desirable to control and enhance the photonic SHE. However, such a goal remains elusive, due to the weak spin-orbit interaction of light, especially for systems with optical loss. Here we reveal a flexible way to modulate the photonic SHE via exceptional points, by exploiting the transverse shift in a parity-time (PT) symmetric system with balanced gain and loss. The underlying physics is associated with the near-zero value and abrupt phase jump of the reflection coefficients at exceptional points. We find that the transverse shift is zero at exceptional points, but it is largely enhanced in their vicinity. In addition, the transverse shift switches its sign across the exceptional point, resulting from spontaneous PT-symmetry breaking. Due to the sensitivity of transverse shift at exceptional points, our work also indicates that the photonic SHE can enable a precise way to probe the location of exceptional point in photonic systems.