Determination of the elastic and piezoelectric constants for crystals in class (3m) is complicated by the large number of independent constants and the many possible ways in which they may be combined. An experimental and analytical procedure has been developed to determine all the constants using primarily thickness-mode measurements made on small, plate-shaped samples of various crystallographic orientations, and results using this procedure have been obtained for lithium tantalate and lithium niobate, two recently developed synthetic crystals. The resonant and antiresonant frequency constants for thickness modes have been calculated as functions of a plate's rotation angle. Information in this form makes possible the selection of plate orientations that might be useful as resonators and transducers.

All of the elastic and photoelastic constants of crystalline lead molybdate (PbMoO4) and various optical and thermal properties of the material have been measured. This information has been used to evaluate the material for a number of practical acousto-optic device applications. The high figure of merit found in earlier preliminary studies is only 10% smaller than the maximum figure of merit of the material. Thus the material is well suited for acousto-optic modulator and deflector applications. However, the material is not particularly useful for tunable acousto-optic filters because the relevant elasto-optic coefficient is small. Acoustic and optical losses, and changes in sound velocity and index of refraction with temperature, can cause operating limitations in practical devices, and these are discussed.

The power extracted from a piezoelectric surface wave in quartz by an arrangement of electrodes on the surface is determined by a perturbation technique, which is extremely accurate for low-coupling materials. The mechanical portion of the surface wave is found by neglecting the piezoelectric coupling, which is very small in quartz. The elastic solution then yields both volumetric and surface source terms, which are generated by the piezoelectric coupling and drive the steady-state electrostatic solution. A technique is introduced for reducing the remaining electrostatic problem to Laplace's equation, subject to such boundary conditions that the solution is amenable to conformal mapping techniques for several interesting, and possibly useful, electrode arrangements. Surface waves propagating along the digonal axis for all rotated Y cuts are considered, as well as those propagating in all directions along the surface of an X-cut crystal. A reciprocal relation between the excitation and detection problems is derived, and is used to determine the amplitude of a surface wave generated by the application of an alternating voltage to the surface electrodes when the solution to the detection problem for the same arrangement of electrodes is known.

No abstract

No abstract