Architecture for On-Chip Acousto-Optic Modulator

An integrated acousto-optic modulator operates with an extremely high extinction ratio (e.g.,>50 dB) thanks to two widely separated two-dimensional (2D) waveguides. These 2D waveguides are formed on or adjacent to a one-dimensional (ID) wave-guide far enough apart (e.g., 10-100 pm apart) to prevent evanescent coupling between them. An acoustic transducer formed on the surface of the ID waveguide switches light from one 2D waveguide to the other 2D waveguide via the ID waveguide. The acoustic wave emitted by the acoustic transducer forms a traveling grating that overlaps with one 2D waveguide. diffracting light from that 2D waveguide into the ID waveguide, which guides the light to the other 2D waveguide. A lateral grating coupler diffracts this light from the ID waveguide into a mode guided by the other 2D waveguide. This acoustic modulator acts as a switch suitable for use in quantum and atomic systems.