Plasmonic-enhanced surface acoustic wave-photonic devices on silicon

Abstract

Surface acoustic waves (SAWs) support long group delays and analog signal processing as part of electronic circuits for decades. SAWs may also be introduced to integrated silicon photonic circuits, through thermo-elastic actuation: the absorption of modulated pump light in gratings of metallic elements. Microwave-rate information is thereby converted from the modulation of an optical carrier to heat representation, and then to SAWs. Information is recovered in the optical domain through photo-elastic modulation of a second carrier wave in a standard silicon-photonic circuit. The biggest drawback of the SAW-photonic integrated devices is the relative inefficiency of thermo-elastic actuation, which leads to large losses of microwave-frequency electrical power between input and output: on the order of 70 dB. In this work, we report the enhancement of actuation through surface-plasmon resonance effects. The metallic grating elements are split to resonant unit cells, designed for maximum absorption of pump light. End-to-end power losses are reduced to only 48 dB. The results highlight the prospects of SAW-photonics as potential platform for integrated signal processing