Abstract
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.
Highlights
Active photonic devices featuring compact size and a large, rapid, and energy efficient optical response are essential to nanophotonic technologies incorporating reconfigurable filters, lasers, photonic networks, optical memories, and optical modulators
While silicon remains the preferred platform for large-scale manufacturing and provides natural advantages for optoelectronic integration, silicon suffers from limited dynamic optical functionality owing to its indirect band gap and modest electro-optic and nonlinear responses
Electro-absorption effects in germanium [7] and graphene [8] have been used to construct broadband optical modulators operating above GHz speeds; these devices are still tens of microns in length, and not suitable for on-demand optical routing, filtering, or all-optical switching
Summary
Active photonic devices featuring compact size and a large, rapid, and energy efficient optical response are essential to nanophotonic technologies incorporating reconfigurable filters, lasers, photonic networks, optical memories, and optical modulators. Electro-optic or nonlinear effects in silicon can be used in modulators or optical logic components, for example, but this typically requires long-path-length interferometers [1] (mm scale) or very narrow band resonators [2, 3] (less than 15 GHz), which are extremely sensitive to thermal or ambient fluctuations and fabrication errors. Circumventing these challenges and realizing devices with improved functionality continues to be a central aim of nanophotonics research. Silicon-organic hybrid geometries can provide all-optical and ultrafast operation capabilities [9, 10], but require very long (100 μm to several mm) interaction lengths even in waveguides with very high nonlinear waveguide parameters (γ > 105 W−1 km−1) or slow-light effects [11]
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