High-efficiency acousto-optical interaction in phoxonic nanobeam waveguide

We demonstrate the simultaneous existence of slow photonic and phononic modes in phoxonic nanobeam. The phoxonic nanobeam is formed by arranging air semi-cylinders along lateral sides of a suspended silicon waveguide. Because of the slow group velocities, the acousto-optical interactions are dramatically enhanced. The efficiencies of interaction are strongly related to the polarizations of both slow photonic and phononic modes. Our proposed structure is a potential high-efficiency acousto-optical modulator with ultra-small footprint size. The operating optical wavelength is about 1550 nm, while the acoustic frequency is about 6.8 GHz.