Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition.

Vanadium dioxide (VO(2)) is a promising reconfigurable optical material and has long been a focus of condensed matter research owing to its distinctive semiconductor-to-metal phase transition (SMT), a feature that has stimulated recent development of thermally reconfigurable photonic, plasmonic, and metamaterial structures. Here, we integrate VO(2) onto silicon photonic devices and demonstrate all-optical switching and reconfiguration of ultra-compact broadband Si-VO(2) absorption modulators (L < 1 μm) and ring-resonators (R ~ λ(0)). Optically inducing the SMT in a small, ~0.275 μm(2), active area of polycrystalline VO(2) enables Si-VO(2) structures to achieve record values of absorption modulation, ~4 dB μm(-1), and intracavity phase modulation, ~π/5 rad μm(-1). This in turn yields large, tunable changes to resonant wavelength, |Δλ(SMT)| ~ 3 nm, approximately 60 times larger than Si-only control devices, and enables reconfigurable filtering and optical modulation in excess of 7 dB from modest Q-factor (~10(3)), high-bandwidth ring resonators (>100 GHz). All-optical integrated Si-VO(2) devices thus constitute platforms for reconfigurable photonics, bringing new opportunities to realize dynamic on-chip networks and ultrafast optical shutters and modulators.