Takaya Watanabe

Leaky Surface Wave Propagating on LiTaO3 Substrate

The propagation characteristics of leaky surface wave on LiTaO3 substrate were investigated for all propagation directions and arbitrary cuts, and the zero slope temperature cuts were discovered. If the Rayleigh wave propagation is used, the zero slope temperature cut does not exist and the minimum value of TCD is 18 [ppm/°C].

A New Cut of LiNbO 3 with Zero Slope Temperature by a Leaky Surface Wave

The propagation characteristics of a leaky surface wave on LiNb03 were theoretically calculated by changing Eulers angle, and the theoretical contour maps for the SAW velocity, el ctromechanical coupling constant K , and temperature deviation of the time delay (TCD) were displayed. From these results, a theoretical new cut with zero slope temperature coefficien3 of delay was discovered. The value of K obtained is as large as 14.7%, which is in good agreement with the experiments at this cut. Velocity is also in good agreement with experiments and is equal to 4419m/s. However, the experimental temperature coefficient was 50 ppm/OC which was not in agreement with theory and was a small value if compared with a normal cut on LiNb03. 5

Zero Slope Temperature SiO 2 /LiTaO 3 Structure Substrate for Stoneley Waves

Theoretical and experimental results on Stoneley waves along an interfacebetweenLiTaO3 and Si02 are presented. Stoneley waves can exist only when the material constants of a piezoelectric material and an isotropic material satisfy particular conditions which we presented previously at the 1983 IEEE Ultrasonics Symposium. The combination of LiTaO3 and Si02 was selected by the results. After the cut angle and propagation direction of LiTaOj with Si02 were determined by the calculated characteristics, an experiment was performed. The measured values were found to be in good agreement with the theory; zero slope temperature (TcD=O) and higher coupling coefficient (K2=1.5%) were obtained with Stoneley waves in the Si02/X-l4BoY LiTa03 structure. These results lead us to expect that future SAW devices could be made without any package.

Zero Slope Temperature SiC/SiO2/LiTaO3 Substrate for Boundary Acoustic Waves

Zero slope temperature SiO2/X-148°Y LiTaO3 substrate has been proposed for use in packageless SAW devices. However, the SiO2 film is required to be about three times the wavelength and, therefore, is easily removed by temperature variation. In this paper, SiC overcoat on SiO2 to reduce the film thickness is proposed. The calculated energy concentration to the middle layer is better than the two media structure. The experimental result agreed with the theory and zero slope temperature was obtained when the total thickness of SiC and SiO2 was about 2.5 times the wavelength.

A New Electrooptic Light Deflection Phenomenon

A new electrooptic light deflection phenomenon has been investigated. This is presumably due to the spatial distribution in the refractive index, induced by the nonuniform electric field under the surface electrodes. 100% deflection efficiency is attained and a large deflection angle can be provided at low driving voltage, either AC or DC. This phenomenon was observed in various materials, including crystals and glasses.