High-sensitivity laser-based acoustic microscopy using a modulated excitation source

A high-sensitivity photoacoustic microscopy system that uses an amplified electroabsorption modulated laser source for excitation was discussed. The system was found to be capable of detecting displacements in the femtometer range at frequencies up to 200 MHz. It was found that the detection bandwidth reduction afforded by this technique allows for a significant improvement in signal-to-noise ratio over systems using pulsed-laser excitation and broadband detection. It was suggested that the high sensitivity of the system makes it well suited for the characterization of thin films and micro- and nanoscale systems.