Yoshiaki TOKUNAGA, Masaki SUZUKI¹, and Masashi IMAI¹

Optoelectronics Device System Research and Development Center, Kanazawa Institute of Technology, Ishikawa 921-8501, Japan
¹Graduate School of Electrical Engineering and Electronics, Kanazawa Institute of Technology, Ishikawa 921-8501, Japan

(Received August 8, 2006; Accepted November 1, 2006)

Unique capability of the second harmonic in a nonlinear surface acoustic wave (NLSAW) generated on 128° Y–X LiNbO₃ substrate was investigated by optical diffraction technique. Amplitudes of the fundamental, the second harmonic, and the third harmonic in it were evaluated from an equation composed as a basis of the Beckmann–Spizzichino model. The experimental findings were as follows: the second harmonic velocity was faster than that of the fundamental; a full width at half maximum in envelope profile of the second harmonic was unchanged as if it experienced the gold thin film; total peak intensity in the envelope profile of the second harmonic during collision at gold thin film area was stronger than the sum of individual peak intensity of two second harmonics before the collision. From our experimental findings we conclude that the second harmonic has a soliton-like characteristic.

Key words: nonlinear surface acoustic wave, SAW velocity, gold thin film, LiNbO₃ crystal, light diffraction method, second harmonic collision, soliton