Pulsed Photoacoustic Materials Characterization

Photothermal Techniques in Material Characterization Applications

“…Extensive reviews of the PA generation and detection for spectroscopy and other measurements have been given in the literature, e.g., Rosencwaig [5] (1980), Patel and Tam [6], Tam [1], and Hutchins and Tam [7]. Most earlier work emphasized the use of the PA technique as a convenient spectroscopic tool for highly transparent, opaque, or light-scattering samples.…”

“…Less noticed so far is the special advantage of P A generation method to produce a single ultra-narrow acoustic pulse with well-defmed pulse shape and no ringing. This was proposed as a mechanism to generate standard acoustic profiles, since the pulsed PA emission shape can be theoretically modelled in detail [7,8]. An experimental arrangement to detect nanosecond PA pulse shapes is shown in Fig.…”

A New Method for Calculation of Laser-Generated Ultrasound Pulses

“…Current applications are to nondestructive evaluation and materials characterization, where it is convenient to have a highly reproducible source requiring no contact with the samplP [2][3][4][5]. The need to make these applications quantitative requires a theoretical model which: 1) is based on fundamental principles; 2) allows the Usf' of realistic sample and source properties; and 3) is readily usable by the research community without a major computational development effort. Doyle [6] and Schliechert et al [7] have described approaches which meet the first two criteria, but which are very computation-intensive.…”

“…One-dimensional models will not suffice: important features of the generated waveforms or.r.nr only when three-dimensional aspects are considered. Scruby et al [12,13] obtained considerable insight from a model invoking equivalent forces to represent a point thermal (surface) source, and Rose [1][2][3][4] has extended that understanding and given it a more rigorous foundation with an Analytical development based on a point temperature (surface) sm1rce. Experimental measurements (see reviews by Hutchins [1] and Hutchins and Tam [3]) are in good agreement, except for the small, positive "precursor" (menti_oned above), the source·of which has not been certain.…”

“…Scruby et al [12,13] obtained considerable insight from a model invoking equivalent forces to represent a point thermal (surface) source, and Rose [1][2][3][4] has extended that understanding and given it a more rigorous foundation with an Analytical development based on a point temperature (surface) sm1rce. Experimental measurements (see reviews by Hutchins [1] and Hutchins and Tam [3]) are in good agreement, except for the small, positive "precursor" (menti_oned above), the source·of which has not been certain. Doyle [6], Schli.echert et al [7], and Telschow and Conant [lS] have attributed this precursor to the finite source dimensions arising from thermal diffusion; however, see below.…”