Abstract
Reconfigurable photonic circuits have applications ranging from next-generation computer architectures to quantum networks, coherent radar and optical metamaterials. Here, we demonstrate an on-chip high quality microcavity with resonances that can be electrically tuned across a full free spectral range (FSR). FSR tuning allows resonance with any source or emitter, or between any number of networked microcavities. We achieve it by integrating nanoelectronic actuation with strong optomechanical interactions that create a highly geometry-dependent effective refractive index. This allows low voltages and sub-nanowatt power consumption. We demonstrate a basic reconfigurable photonic network, bringing the microcavity into resonance with an arbitrary mode of a microtoroidal optical cavity across a telecommunications fibre link. Our results have applications beyond photonic circuits, including widely tuneable integrated lasers, reconfigurable optical filters for telecommunications and astronomy, and on-chip sensor networks.
Highlights
Most techniques which enable broad tuning of optical cavities can be sorted into two categories
We have reported full FSR electrical tuning of a high quality silicon chip-based optical microcavity
To achieve this we develop a new approach to FSR tuning, combining engineering of the optomechanical interaction to create a highly strain-dependent effective refractive index with electrical actuation through integrated interdigitated capacitors
Summary
Most techniques which enable broad tuning of optical cavities can be sorted into two categories. FSR tuning has been reported with a split-ring microcavity[36], consisting of two evanescently coupled curved waveguides In this case, physically splitting the cavity allows increased mechanical compliance and improved tunability, but introduces inherently large losses that strongly limit the optical quality factor. Whereas most thermal-based approaches rely on changing the effective refractive index neff through the material’s thermooptic coefficient, and most strain-based approaches rely on changing the cavity length L (see Eq 1), it is possible to use the optomechanical interaction to engineer an effective refractive index neff which is very strongly strain-dependent, much beyond the intrinsic photoelastic properties of the material[39,40] This allows far greater tunability to be observed than that achievable through simple physical compression of the cavity. This provides a direct, scalable and low power electronic tuning mechanism
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