USE OF OBLIQUELY CUT PIEZOELECTRIC SEMICONDUCTORS OF CLASS (6MM) CRYSTALS FOR ULTRASONIC AMPLIFIERS

A detailed theoretical analysis and some experiments are given on the use of obliquely cut piezoelectric semiconductors of class (amm) crystals for ultrasonic traveling-wave amplifiers. When a shear ultrasonic wave is amplified in an obliquely cut crystal in which the wave propagates obliquely with the c axis, a considerably higher gain is obtained than that obtained in the normally cut crystal in which the wave propagates normal to the C axis. In obliquely cut crystals, the displacement vector and the energy flux of the ultrasonic wave deviate from those in the normally cut crystals. In general, these deviations vary according to the operating conditions, such as frequency, dc drift field, and conductivity of the crystal. However, in a obliquely cut crystal, the deviation of the displacement vector of the shear wave is small and the deviation of the energy flux of the shear wave does not depend on the operating conditions. As an attempt to utilize these obliquely cut crystals for an ultrasonic amplifier, an ultrasonic-amplifier device with integrated diffusion-layer transducers has been built. The maximum net electrical gain obtained by this device is 15 dB at 100 MHz. © 1969 IEEE. All rights reserved.