Yoshiaki TOKUNAGA, Yukihiro ISHIMARU, Masatoshi YOSHIMURA, Koji AIZAWA, and Akiyuki MINAMIDE¹

Graduate School of Electrical Engineering and Electronics, Kanazawa Institute of Technology, Ishikawa 921-8501, Japan
¹Electrical and Electronic Engineering of Kanazawa Technical College, Ishikawa 921-8501, Japan

(Received September 30, 2009; Revised November 27, 2009; Accepted December 21, 2009)

An estimation methodology for amplitude from the fundamental to fourth-order harmonic composed of nonlinear surface acoustic waves on a LiNbO₃ substrate with a 128° Y–X propagation axis was demonstrated. First, equations for estimation of amplitudes from diffracted light intensity were shown and then numerical simulations of main factors were carried out. Normalized diffraction light intensities due to components of nonlinear surface acoustic waves were measured and their amplitudes were obtained from measured values. Finally, the amplitude of the second harmonic propagating on a gold thin film of about 50 nm thickness was estimated. It was found that the amplitude of the second harmonic increased continuously from 0.8 to 2.0 Å with propagation distance in the thin film.

Key words: nonlinear surface acoustic wave, gold thin film, LiNbO₃ crystal, light diffraction method, second harmonic, numerical simulation