SAW propagation on proton-exchanged lithium niobate

A novel method using only the easily measured velocity of SAWs (surface acoustic waves) is demonstrated for determination of elastic constants of anisotropic layers on arbitrarily anisotropic and piezoelectric substrates. The elastic constants and propagation properties of any nonpiezoelectric isotropic, cubic, or even trigonal layer on an arbitrarily anisotropic substrate can be determined with this method. The method was applied to proton-exchanged (PE) lithium niobate in order to determine its as yet unknown elastic constants. Dispersion curves and elastic stiffness constants of PE Y-cut LiNbO₃ have been evaluated. The results are reliable for waveguides fabricated in diluted melts containing 0.25-2.00 mol.% lithium benzoate. Using the obtained elastic-stiffness constants, SAW propagation properties such as power flow, diffraction, and strain distribution can be analyzed in order to achieve sophisticated design of guided SAW and acoustooptic devices based on PE:LiNbO₃ waveguides