Ultrasonic anomalies in the spectrum of acoustic waves diffracted by periodic interfaces

The energy distribution of elastic waves reflected from corrugated periodic solid surfaces is investigated. Broadband pulse echo experiments using ultrasonic spectroscopy are carried out for surfaces with a triangular profile. Sharp discontinuities observed in the received spectrum are interpreted as anomalies first introduced by R. W. Wood [Philos. Mag. 4, 396 (1902)]. These minima are identified as the mode-converted signals along the interface with bulk or surface wave velocities. The observed anomalies may be used to characterize interfaces and quality of bonding.