HIGH-POWER OPTICAL FIBER DELIVERY SYSTEM FOR THE LASER GENERATION OF ULTRASOUND

A plastic-clad optical fiber system has been examined as a delivery system of pulsed laser energy for the generation of ultrasound. The onset of significant optical damage caused by the laser has been investigated. By using multimode fibers of approx. 1 m length with 600 μm core size, it was found that laser power densities from the fiber were sufficient to produce ultrasonic waveforms corresponding to both the thermoelastic and plasma generation regimes. Out-of-plane acoustic displacements of >250 pm can be achieved through 2.5 cm thick aluminum test samples, showing that fiber optical delivery systems may be considered in systems using laser-generated ultrasound for non-destructive testing applications.