Curvature tuning surface phonon polaritons inside the forbidden band of van der Waals crystal using an invertible core–shell heterostructure

Phonon polaritons (PhPs) hold profound significance within the realms of nanophotonics and optoelectronics. Nevertheless, they are characterized by narrow frequency bands and restricted regulatory means. In this research, an innovative approach is proposed, which entails the utilization of phonon heterostructures and curvature engineering to break the forbidden band of van der Waals crystals and enable precise modulation. With the invertible h-BN/polar semiconductor core–shell heterostructure as a case in point, a universal analytical dispersion equation has been derived, thereby disclosing the regular variations in the opening of the bandgap and the characteristics of PhPs in relation to curvature. This breakthrough paves a novel avenue for the regulation of PhPs in nanostructures, exhibits substantial application potential across multiple domains such as superlenses, sub-diffraction imaging, and optical waveguides, and effectively propels the advancement of nanophotonics technology.