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

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 degrees Y-propagating LiNbO3 (LN) thin-plate bonded to a AT-cut 45 degrees 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 mu m and the driving voltage required by the LLSAWs of the 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. (C) 2019 The Japan Society of Applied Physics