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.