Su-Schrieffer-Heeger model in Nano-opto-electro-mechanical device for high optomechanical coupling rate

The Nano-Opto-Electro-Mechanical device consists of an optomechanical (OM) cavity within a phoXonic nanobeam, connected to inter-digitated transducers (IDTs) at both ends to excite and detect acoustic waves. The OM cavity's optical modes are activated by an external waveguide ending in a Bragg mirror made from tapered holes. The phoXonic cavity, designed with periodic holes and stubs, generates both an acoustic bandgap in the GHz range and an optical bandgap around 1550 nm for telecommunications. The device supports acoustic modes from 2 to 4 GHz and optical modes with high-quality factors, demonstrating a substantial optomechanical coupling rate (g) on the MHz scale. We also explored phononic cavity modes using IDTs placed in front of the nanobeam. In this work, we investigate high-frequency cavities in the 6–10 GHz range. To achieve this, the design of OM cavities with localized phonon modes is modified by introducing long-length stubs to adjust the frequency and enhance OM coupling. These innovations build on previous designs that controlled phonon frequency by altering hole and stub sizes. Additionally, the study explores topological effects, using the Su-Schrieffer-Heeger (SSH) model to create simultaneous localized acoustic and optical modes at the interface between two different phoXonic crystals, resulting in both photonic and phononic topological interface modes.