Reconfiguring Magnetic Infrared Resonances with the Plasmonic Phase-Change Material In₃SbTe₂

For miniaturized active nanophotonic components like adjustable lenses, resonance tuning of nanoantennas is essential. Phase-change materials (PCMs) have been established as prime candidates for nonvolatile resonance tuning based on a change in the refractive index. Currently, a novel material class of switchable infrared plasmonic PCMs, like In₃SbTe₂ (IST), is emerging. Because IST can be locally optically switched between dielectric (amorphous) and metallic (crystalline) states, it becomes possible to directly change the geometry and shape of nanoantennas to tune their infrared resonances. Here, crystalline IST split-ring resonators (SRRs) are directly optically written and reconfigured to continuously tune their magnetic dipole resonance wavelengths from 10.6 to 8.2 μm without changing their electric dipole (ED) resonances. The SRRs are further modified into crescents and J-antennas, displaying electric quadrupole and rotated ED modes, respectively. Our concepts may be well suited for rapid prototyping, speeding up workflows for engineering ultrathin, tunable, plasmonic devices for infrared nanophotonics.