Abstract: Disclosed is an apparatus and method for nondestructive testing of structures where the apparatus includes a transducer for generating an ultrasonic acoustic signal, a nonlinear medium for parametrically generating a special, ramp, waveform, and an acousto-optic broadband receiver for detecting a reflected signal from the test structure. A homodyne interferometer is provided to measure the change of refractive index of the acousto-optic receiver, and generates an electrical signal representative of the reflected acoustic signal. Signature analysis techniques are utilized to evaluate the reflected waveform to determine the characteristics of the structural defects.