A novel technique for enhancing the signal to noise of laser - Based ultrasonic systems

Oluwaseyi Balogun*, Nicholas Pratt, Todd W. Murray

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


Conventional laser ultrasonic systems use pulsed laser sources to generate broadband acoustic waves. The theoretical signal to noise ratio (SNR) of these systems, in the shot noise limit, is inversely proportional to the square root of the bandwidth of the detection system. Previous researchers have shown that improvements in the SNR can be made by generating narrowband acoustic signals using temporally and/or spatially modulated laser pulses, and reducing the detection bandwidth accordingly. In this work, the generation of high frequency acoustic waves using an amplitude modulated continuous wave (CW) laser is demonstrated. The acoustic signals are detected using a path stabilized Michelson interferometer coupled to an RF lock-in amplifier. This allows for control of the detection bandwidth, which can be reduced by several orders of magnitude below typical broadband laser ultrasonic systems. Experimental results showing CW generated acoustic waves in various material systems are given. The magnitude and phase of the acoustic signals in the frequency domain are detected with an interferometer/lock-in amplifier system, and these data are in turn processed to synthesize the time domain response. The use of narrowband generation/detection combined with subsequent time domain reconstruction allows for a large increase in SNR without losing the ability to distinguish individual acoustic arrivals or modes in the time domain.

Original languageEnglish (US)
Title of host publicationProceedings - 2004 IEEE Ultrasonics Symposium
Subtitle of host publicationA Conference of the IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Society, UFFC-S
EditorsM.P. Yuhas
Number of pages4
StatePublished - Dec 1 2004
Event2004 IEEE Ultrasonics Symposium - Montreal, Que., Canada
Duration: Aug 23 2004Aug 27 2004


Other2004 IEEE Ultrasonics Symposium
CityMontreal, Que.

ASJC Scopus subject areas

  • Engineering(all)

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