On-chip 7 GHz acousto-optic modulators for visible wavelengths

A chip-integrated acousto-optic phase modulator tailored for visible wavelengths has been developed. Utilizing the lithium niobate on sapphire platform, the modulator employs a 7 GHz surface acoustic wave, which is excited by an interdigital transducer and aligned perpendicular to the waveguide. This design achieves efficient phase modulation of visible light within a compact device length of 200 micrometers and holds the advantages of easy fabrication and high stability due to its simple unsuspended structure. In this high-frequency acoustic regime, the acoustic wavelength becomes comparable to the optical wavelength, resulting in pronounced single-sideband modulation behaviors. This observation underscores the phase delay effects in the acousto-optic interactions, and enables new opportunities for developing functional visible photonic devices and their integration with atom- and ion-based quantum platforms.