Y. Tsukahara et al., LONGITUDINAL CRITICAL ANGLE SINGULARITIES AND THEIR EFFECT ON V(Z) OFTHE LINE-FOCUS-BEAM ACOUSTIC MICROSCOPE, IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 41(4), 1994, pp. 458-466
In order to investigate a mechanism which causes a velocity difference
between the longitudinal wave and leaky surface skimming compressiona
l wave (LSSCW) observed in a line-focus-beam acoustic microscope, the
analytic property of an acoustic reflection coefficient and its effect
on a V(z) analysis were studied. A pole hidden in the unphysical Riem
ann sheet close to the longitudinal branch point is found to be respon
sible for the abrupt phase change at the longitudinal critical angle.
This, together with an effect of a dominant Rayleigh wave pole, affect
s the V(z) measurement of the LSSCW. A method to estimate the longitud
inal and shear wave velocities is discussed.