Byung-II Noh
Auburn University, Auburn, Alabama, USA _______________________________________
Electromagnetic hyperbolicity, with access to sub-diffraction optics and high photonic density of states, has driven key functionalities in nanophotonics, including super-resolution imaging, efficient energy control, and extreme light manipulation. Central to these advances are hyperbolic polaritons—nanometer-scale light-matter waves—spanning multiple energy-momentum dispersion orders with increasing optical momenta. While high-order hyperbolic polaritons offer superior optical confinement, their excitation and manipulation are challenging compared with their low-momentum zeroth-order counterpart. In this work, we report the mode conversion of hyperbolic polaritons at different orders by breaking the structure symmetry in engineered step-shape van der Waals (vdW) terraces. The converted high-order hyperbolic polaritons are imaged by scattering-type scanning near-field optical microscopy (s-SNOM). Our s-SNOM data, augmented with electromagnetics simulations, further demonstrate the alteration of polariton mode conversion by engineering the vdW terraces. The mode conversion reported here provides a practical approach to harnessing previously hard-to-access high-order hyperbolic polaritons with extremely high momenta towards promising applications in nano-optical circuits, sensing, computation, information processing, and super-resolution imaging.
Email: bzn0023@auburn.edu