Nonreciprocal Goos-Hänchen and photonic spin Hall shifts driven by incident angle and polarization at a planar interface

Most studies on Goos-Hänchen and photonic spin Hall beam shifts are focused on reciprocal, or direction-independent, beam shifts. In this work, we present a strategy to induce nonreciprocal beam shifts in the reflected field from a planar heterostructure by exploiting direction- and polarization-dependent coupling between the incident field and the structure. We show that the heterostructure's resonant modes lead to polarization-dependent, nonreciprocal reflection at specific incident angles. This behavior enables controlled tuning of the direction-dependent transformation of optical momentum. Consequently, we observe nonreciprocal Goos-Hänchen and photonic spin Hall shifts in the reflection plane, manifesting as lateral and transverse displacements, respectively. These shifts arise from the conversion of linear momentum and orbital angular momentum into spin angular momentum. The results are verified using three independent approaches—comsol multiphysics simulations, the stationary phase method, and Gaussian beam scattering calculations—with excellent agreement among them.