Laser-based ultrasound arrays for generation and detection of narrowband, single mode Lamb waves

Single mode Lamb waves can be generated by using a periodic spatial array of laser sources that can also be periodically pulsed in time. This technique allows selection of particular operating points on various modal curves in the Lamb wave dispersion mode diagrams. Results presented compare the experimentally measured and numerically calculated Lamb wave dispersion curves for both antisymmetric and symmetric modes from zeroth to fifth order and allow inference of generation efficiency and dispersion associated with a specific operating point. The laser generation and detection technique described here can lead to the rapid scanning of the transduction region over the material´s surface and selection of a specific operating point that is associated with a high generation efficiency and low frequency dispersion. The laser generation and detection of narrowband low dispersion pulses obtained from a selected operating point is demonstrated. The suitability of using this technique for selecting specific modes for NDE applications in plate-like structures is described