Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT)
since certain modes at various center frequencies are sensitive to specific types of defects. Ideally
one should be able to select both the mode and the center frequency of the launched waves. We
demonstrated that an affordable laser diode array can selectively launch either the S0 or A0
ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode
array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching
the selected mode and frequency was employed between the output of the elements. The generated
ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits
non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust
in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.peerReviewe