Abstract:

Phonon polaritons are hybrid quasiparticles arising from the coupling between infrared photons and lattice vibrations, enabling strong subwavelength confinement of electromagnetic fields. This unique property makes them highly promising for nanoscale manipulation of infrared light and enhanced light–matter interactions. In this work, we theoretically investigate hyperbolic phonon polariton in various boron nitride (BN) systems. Van der Waals heterostructures are constructed by combining different BN materials, including h10BN, h11BN, pyrolytic boron nitride, and wurtzite boron nitride, and further integrated with α-MoO₃. We systematically analyze the effects of material composition, stacking sequence, and layer thickness on polariton dispersion, interlayer coupling, and interfacial hybridization. The influence of isotopic mass variation, crystal disorder–induced damping, and phase-dependent dielectric responses is first examined through intrinsic dispersion comparisons. Our results reveal that multilayer BN heterostructures enable tunable mode hybridization, leading to dispersion reconstruction, including branch rearrangement and spectral redistribution. When coupled with α-MoO₃, the system exhibits multiple dispersion bandgaps and low group-velocity branches under specific conditions, arising from strong multimode coupling. These findings demonstrate that material selection, stacking configuration, and thickness engineering provide versatile degrees of freedom for tailoring hyperbolic phonon polaritons, offering valuable theoretical guidance for infrared polariton engineering in complex van der Waals heterostru

Key words: phonon polaritons, isotopic boron nitride, van der Waals heterostructures, negative refraction, mode hybridization, slow light