Acousto-optic modulators driven by longitudinal leaky surface acoustic waves on LiNbO3 thin-plate bonded structures

Abstract

To obtain an acousto-optic modulator (AOM) driven by a longitudinal leaky surface acoustic wave (LLSAW) with a low driving voltage and a high diffraction efficiency, proton-exchanged planar optical waveguide-type AOMs with structures consisting of an X-cut 36°Y-propagating LiNbO3 (LN) thin-plate bonded to a AT-cut 45°X-propagating quartz or c-plane sapphire (Al2O3) substrate were fabricated and their diffraction properties evaluated. The maximum diffraction efficiency in the zeroth transverse electric (TE0) mode optical guided wave with an optical wavelength of 0.633 μm and the driving voltage required by the LLSAWs of the AOMs were 91% and 5.1 VRMS for LN/quartz and 60% and 11 VRMS for LN/Al2O3, respectively. The diffraction properties of the LLSAWs on the bonded structures were improved compared with those on a single LN substrate.