Metamorphosis of bulk waves to Lamb waves in anisotropic piezoelectric crystals

Acoustic bulk waves were excited by local electric field probe in an anisotropic piezo-electric crystal Lithium Niobate (X-cut). A narrow pulse with a width of 25 ns was used for excitation to obtain wide frequency content in the Fourier domain. A wide spectrum ensures metamorphosis of bulk waves into Lamb waves for scan lengths comparable to the involved wavelengths. The low frequency content experiences multiple reflections from the two surfaces of the plate and disperses along the propagation direction. Acoustic bulk wave's evolution and transformation to Lamb waves are illustrated and explained with the aid of the Lamb wave dispersion phenomenon. The holographic images in the Fourier domain exemplify the metamorphosis of waves during propagation following the excitation at an approximate point source.