CHARACTERISTICS OF SURFACE ACOUSTIC-WAVES ON PROTON-EXCHANGED AND ANNEALED PROTON-EXCHANGED Z-CUT LINBO3 USING PYROPHOSPHORIC ACID

The characteristics of surface acoustic waves (SAWs) on proton-exchanged (PE) and annealed proton-exchanged (APE) Z-cut Y-propagated LiNbO3 waveguides using pure pyrophosphoric acid are investigated and compared. The distribution of hydrogen in the PE samples measured by secondary-ion mass spectrometry (SIMS) shows a step-like profile with the diffusion constant D-0 and the activation energy Q of about 9 x 10(7) mu m(2)/h and 82.18 kJ/mol, respectively. The velocity (V-p) of SAW on PE samples decreases with the increase of kd, where k is 2 pi/lambda and d is the waveguide depth, and almost exhibits an exponential decay. However, post-annealing will result in a restoration of the decreased velocity and an improvement of the SAW insertion loss (IL). On the other hand, the electromechanical coupling coefficient (K-2) almost decreases with the increase of kd and shows greater sample-to-sample discrepancy.