Actively tuning anisotropic light-matter interaction in biaxial hyperbolic material α-MoO3 using phase change material VO2 and graphene

Abstract Anisotropic hyperbolic phonon polaritons (PhPs) in natural biaxial hyperbolic material α -MoO 3 has opened up new avenues for mid-infrared nanophotonics, while active tunability of α -MoO 3 PhPs is still an urgent problem needing to be solved. In this study, we present a theoretical demonstration of actively tuning α -MoO 3 PhPs using phase change material VO 2 and graphene. It is observed that α -MoO 3 PhPs are greatly dependent on the propagation plane angle of PhPs. The insulator-to-metal phase transition of VO 2 has a significant effect on the hybridization PhPs of the α -MoO 3 /VO 2 structure and allows to obtain an actively tunable α -MoO 3 PhPs, which is especially obvious when the propagation plane angle of PhPs is 90°. Moreover, when graphene surface plasmon sources are placed at the top or bottom of α -MoO 3 in α -MoO 3 /VO 2 structure, tunable coupled hyperbolic plasmon–phonon polaritons inside its Reststrahlen bands (RBs) and surface plasmon–phonon polaritons outside its RBs can be achieved. In addition, the above-mentioned α -MoO 3 -based structures also lead to actively tunable anisotropic spontaneous emission (SE) enhancement. This study may be beneficial for the realization of active tunability of both PhPs and SE of α -MoO 3 , and facilitate a deeper understanding of the mechanisms of anisotropic light-matter interaction in α -MoO 3 using functional materials.