Breaking the sensitivity barrier: The challenge for laser-ultrasonics

The utility of laser ultrasonic methods outside of the laboratory has been limited by the poor sensitivity of this optical technology relative to its contact piezoelectric counterpart. Recent modifications to improve laser ultrasonic sensitivity have included alterations to interferometric detection systems, the use of high peak power pulsed lasers for detection, spatial and temporal modulation of the interrogating beam, and modulation of the source laser in time or in space to narrow the acoustic signal bandwidth, in addition to a handful of more experimental approaches. The issues discussed include detectability, maximizing surface displacement, increasing reflected light power, and decreasing bandwidth