“…Stampfli et al [44] and Newacheck et al [45] used the two-wave mixing PRC interferometer to concurrently measure in-plane and out-of-plane displacement components in a multiferroic composite structure subjected to sinusoidal electric AC field (30 kHz or 32.5 kHz). To increase the SNR, the surface was sanded to remove marks and scratches and then polished to near mirror finish prior to measurement using the interferometer [45] .…”