Tailoring Phonon Polaritons in hBN with the Plasmonic Phase-Change Material In₃SbTe₂

Polaritons in van-der-Waals materials (vdWMs) promise high confinement and multiple tailoring options by resonators and launching structures which conventionally require cumbersome lithography techniques. Optical programming of phase-change materials (PCMs) offers fast and reconfigurable fabrication of these structures. As the plasmonic PCM In₃SbTe₂ can be switched between a dielectric and metallic phase, In₃SbTe₂ is promising for optical programming of metallic launching structures to tailor and confine polaritons in vdWMs. Here, we combine the vdWM hexagonal boron nitride (hBN) with In₃SbTe₂ and optically program circular resonators for hBN's phonon polaritons into In₃SbTe₂. We investigate the polariton resonators with near-field optical microscopy. Demonstrating the reconfigurability, we decrease the resonator diameter to increase the confinement up to λ/39 and achieve a quality factor of 72. Finally, we fabricate a focusing structure for hBN's polaritons whose focal point we reconfigure. We promote In₃SbTe₂ as a versatile platform for rapid prototyping of polariton optics in vdWMs.