3E-2 New Properties of the Anisimkin Jr.´ Modes in Quartz Plates

Dispersion curves, coupling constants, surface displacements, and displacement profiles are numerically calculated for acoustic plate modes, propagating in fused and Y-rotated, X-cut quartz with thickness h/lambda in the range 0 - 4.5 (h, thickness, lambda, wavelength). Four Anisimkin Jr.´ modes with velocity v_nmiddot close to that of longitudinal bulk wave v_L and dominant longitudinal displacement u₁ distributed uniformly through the plate thickness are found in the crystal with cut angles mu = 120deg-140deg and plate thickness h/lambda = 0 - 0.36, 0.94 - 1.78, 2.32 - 3.08, and 3.64 - 4.44. Velocities v_n are varied within plusmn 0.5 %. The coupling constants K_n ² decrease with mode order n and h/lambda, approaching maximum 0.475 % for n = 0 at h/lambda = 0.2. The same modes in fused quartz are not found, except in a narrow region near zero thickness.