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For miniaturized active photonic components, resonance tuning of nanoantennas is essential. Phase-change materials (PCMs) have been established as prime candidates for non-volatile resonance tuning based on a change in refractive index [1]. Currently, a novel material class of switchable infrared plasmonic PCMs, like In3SbTe2 (IST), is emerging. Since IST can be locally optically switched between dielectric (amorphous phase) and metallic (crystalline phase) states in the whole infrared range, it becomes possible to directly change the geometry and size of nanoantennas to tune their infrared resonances by more than 4 µm. In particular, resonant nanostructures on sub-meta-atom level can be directly written, erased and modified in the thin IST film without cumbersome nanofabrication techniques. Additionally, prepatterned nanoantennas can be screened by a thin IST film resulting in an on/off functionality. With an IST patch two nanoantennas can be soldered together to shift the resonance [2].
Here, crystalline IST split-ring resonators (SRRs) are directly optically written and reconfigured in their arm size to continuously tune their magnetic dipole resonances over a range of 2.4 µm without changing their electric dipole resonances. The SRRs are further modified into crescents and J-antennas, which feature more complex resonance modes dependent on the polarization of the incident light. The ability of erasing and modifying the structures enables reversible and fast adaptions of the fabricated antenna geometries. In addition, the experimental results and the corresponding mode assignments are confirmed with full-wave simulations [3]. Our concepts are well-suited for rapid prototyping, speeding up workflows for engineering ultrathin, tunable, plasmonic devices for infrared nanophotonics, telecommunications or (bio)sensing.
[1] Wuttig et al., Nature Photonics 11, 465 (2017)
[2] Heßler et al., Nature Communications 12, 924 (2021)
[3] Heßler, Conrads et al. Nano Letters (submitted) (2021)
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