ECCS-EPSRC Micromechanical Elements for Photonic Reconfigurable Zero-Static-Power Modules

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Integrated photonics has developed by leaps and bounds over the past decade and has seen widespread application far beyond the originally envisioned domain of telecommunications. For instance, the recent funding rounds raised by photonics startups Lightmatter and PsiQuantum, point to the fact that integrated photonics is expected to play a key role in the development of hardware for both artificial intelligence and quantum computing.In spite of all this progress and promise, there is one key problem that has remained unaddressed. For photonics to realise its promise, both in terms of scale and energy efficiency, it requires the use of high quality factor resonators, devices in which light can circulate for long periods with low-loss. While there has been great progress in reducing the propagation loss in photonic devices, the inherent fabrication variation present even in state of the art foundry processes, makes it impossible to design nominally identical devices for implementing any given function. This means that some method for post fabrication compensation and tuning must be utilised. While several such approaches for tuning currently exist, all of them either require large steady state energy consumption (thermal tuning) or large on-chip footprint (MEMS tuning). What is ideally needed is a mechanism that allows a resonator's frequency to be tuned post-fabrication where the tuning mechanism is both small footprint and efficient (zero static energy dissipation). This project is designed to address this goal by exploiting mechanically bistable structures that can be flipped between two stable states to induce the tuning. We will develop switchable, digital (step-by-step), nonvolatile (no static power dissipation) micromechanical tuning elements for adjusting the resonant wavelength of integrated photonic resonators after fabrication. These tuning elements will be selectively and permanently switched to digitally tune resonators into alignment with each other, eliminating the need to apply a persistent, resonator-specific tuning to compensate for fabrication variations. We will demonstrate that these mechanically bistable elements can be designed and fabricated in a state of the art foundry process, and also show the stability of operation from room temperature down to 4K. Our main goal is to show that by using this tuning method, we can reduce the 'effective' fabrication variation by ~10x, and enable a new generation of integrated photonic devices, designed around high-Q resonators.