The Investigation of Polariton Reflection Phase in Hexagonal Boron Nitride

Polaritons – confined light-matter waves – in van der Waals (vdW) materials has been a research frontier in light-matter interactions with demonstrated nanophotonic advances that are unprecedented in conventional systems. Reflection, as a fundamental property of waves, is of particular importance for vdW polaritons, predominantly because it enables the imaging and investigations of polariton standing waves using the scanning probe technique. While all previous works demonstrate a rigid phase ~ π/4 for the polariton reflection, we report altering of polariton reflection phase by varying the geometry of polaritonic microstructures in the case study of hyperbolic surface polaritons in hexagonal boron nitride. The polariton reflection phase can be systematically altered by varying the corner angle of hBN microstructures, and even reveals a π jump around a specific angle. We further demonstrated that our results on vdW polaritons follow a mathematic axiom that should govern all complex physical parameters.