Photonic Spin Hall Effect in Robust Phase Gradient Metasurfaces Utilizing Transition Metal Nitrides

Robust and high-temperature stable (refractory) transition metal nitrides are an emerging class of nanophotonic materials aimed at durable, bio- and CMOS-compatible plasmonic and metasurface applications. In this work, we experimentally demonstrate titanium nitride- and zirconium nitride-based phase manipulating optical metasurfaces that exhibit a photonic spin Hall effect. In the developed all-nitride system, metal nitrides are combined with dielectric nitrides such as aluminum nitride and silicon nitride to design a highly anisotropic, multilayer resonator geometry that supports gap plasmons and enables high power efficiency (similar to 40%) and broad bandwidth of operation in the near-infrared wavelength region. A one-dimensional phase gradient created by geometric rotations of the resonators leads to simultaneous, spatial separation of right and left circular polarization as well as different frequency components of the incident light. This work shows that transition metal nitrides can be successfully integrated into efficient metasurface building blocks for planar, rugged optical devices.