Optical Observation of Elastic Resonances in NH4H2PO4

摘要

Elastic resonances in NH4H2PO4 (ADP) have been studied by an optical method which depends on the elasto‐optic effect. Displacement models of the overtone resonance modes have been inferred from the optical patterns. For a (zxt) 45° plate, the transmission patterns for the stronger resonances are consistent with the picture of two longitudinal standing waves traveling at right angles; the reduced frequency constants are independent of the mode number m, and the sample resonates as m2 Lamé plates. For a (zxt) 0° plate, the greater part of the transmission patterns can be explained in terms of two shear standing waves traveling at right angles; the reduced frequency constants depend on the mode number n, but they tend to become constant as n increases. For both types of plate, the configuration of the electrodes is important in determining which modes are excited and to what extent.