Acousto-Optic Modulators Driven by Longitudinal Leaky Surface Acoustic Waves on Bonded Structures

In this study, to obtain an acousto-optic modulator (AOM) driven by a longitudinal leaky surface acoustic wave (LLSAW) with a lower driving voltage and a higher diffraction efficiency, proton-exchanged optical-waveguide-type AOMs with structures consisting a LiNbO₃ (LN) thin plate bonded to a quartz or sapphire (Al₂O₃) substrate were fabricated and their diffraction properties were evaluated. The maximum diffraction efficiency in the TE₀ mode with an optical wavelength of 0.633 μm and the driving voltage required by the LLSA Ws of AOMs were 91 % and 5.1 V_RMS for LN/quartz and 60% and 11 V_RMS for LN/Al₂O₃, respectively. The diffraction properties of the LLSAWs on the bonded structures were improved compared with those on a single LN substrate.