Yoshiaki Tokunaga

Study on Photopyroelectric Signal of Optically Opaque Material Measured by Polyvinylidene Difluoride Film Sensor.

In this paper, we propose a new one-dimensional model to analyze a photopyroelectric signal of optically opaque materials measured by a polyvinylidene difluoride (PVDF) film sensor. This model is considered three layers (sample, air gap and the PVDF film) and the reflections of the thermal wave at the interfaces of each layer. In order to check the validity of the proposed model, we measure the inclination of the frequency dependence of the signal measured by the PVDF film and compare it with a theoretical value. When laser light is irradiated onto a graphite surface on the PVDF film, the measured inclinations are -1.6 for a 9 µm PVDF film, -1.8 for a 28 µm film and -2.0 for a 110 µm film. These inclinations were comparable with the simulated inclinations in the cases of all the film thickness of the PVDF film considered.

Material evaluation with new modulation method in photoacoustic technique

The proposed new method partially solves the problem of low signal-to-noise-ratio (SNR) when modulation frequency increases. In this paper, the authors suggest keeping the amplitude of the detected photoacoustic (PA) signal constant by linearly increasing the modulation voltage versus the frequency. This technique decreases the SNR at low frequencies but increases the SNR in the usual noisy band and the PA signal of the sample can be easily estimated by FFT. Furthermore, the technique is demonstrated to effectively detect a subsurface defect in a graphite sample in the 10–100 Hz frequency range.

P1L-4 A Unique Capability of a Second Order Harmonic in the Nonlinear Surface Acoustic Wave

Historically, the second harmonic in the NLSAW has never been systematically and thoroughly investigated because research until now has been based on the concept of reductionism. From the new scientific viewpoint, we attempt to study a unique capability of a second harmonic in the nonlinear surface acoustic wave (NLSAW). The remarkable characteristics of the second harmonic, in comparison with those of the fundamental one, were investigated