Optimizing optomechanical resonators for ultra-high-frequency timing applications

Optomechanical resonators emerge as a compelling high-performance alternative for GHz timing references, thanks to the intrinsic assets of this transduction over electrical methods. However, timing applications present system-level design challenges necessitating a particular approach to the design of the resonators. Here we present the first study of such constraints, and provide general design guidelines. Starting from the identification of key performance parameters, we explore the relevance of two optomechanical resonator geometries. First, we experimentally study silicon microdisks, which garner significant attention for sensing purposes, unveiling their suboptimal suitability for timing applications. Then we introduce an alternative geometry, based on a ring-like mechanical structure. We elucidate its advantages in terms of quality factor and dynamic range, and clarify its design principles. It is anticipated that the ring-like resonators will exceed existing performance standards for oscillators, thereby facilitating operation across frequency ranges spanning from 1 GHz to 5 GHz.