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

Murray, T. W.; Balogun, O.
October 2004
Applied Physics Letters;10/4/2004, Vol. 85 Issue 14, p2974
Academic Journal
A laser-based acoustic microscopy system has been developed that uses an amplified electroabsorption modulated diode laser for narrow bandwidth acoustic wave generation at frequencies up to 200 MHz. 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. Femtometer range displacement sensitivity is demonstrated, allowing for materials characterization with only minimal surface heating. The source modulation frequency is scanned over the bandwidth of interest and the transient response of the specimen is reconstructed from the frequency domain data. This signal processing approach allows for easy identification of individual acoustic arrivals or multiple acoustic modes.


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