【Member Papers】Xiamen University --- Hyperbolic polaritons in twisted β-Ga₂O₃

      Researchers from the Xiamen University have published a dissertation titled "Hyperbolic polaritons in twisted β-Ga₂O₃" in npj nanophotonics.

Abstract

      Hyperbolic polaritons (HPs) are essential for integrated photonics due to their directional propagation and strong field confinement. While most research focuses on in-plane light behavior, the out-of-plane features of HPs remain underexplored. In this work, we theoretically predict a novel light coupling mechanism in twisted β-Ga₂O₃ bilayers, involving both surface and volume HPs. As the twist angle increases, the polaritons merge, transitioning from a “four-wing” to a “two-wing” state, accompanied by changes in the iso-frequency contours (IFCs). This shift in dispersion and field distribution results from the interaction between surface and volume HPs, wherein they exchange energy and modify their vertical locality. We also introduce a method for analyzing mode interactions via wavevector collinearity. Our work extends twistronics to control the vertical locality of polaritons, enabling new possibilities for sub-wavelength light manipulation with applications in super-resolution imaging, nanophotonics, and compact photonic devices.