Photoacoustic study of the transmission of wide-band ultrasonic signals through periodic one-dimensional structures

The propagation of wide-band acoustic pulses in one-dimensional periodic st ructures consisting of alternating plexiglas and water layers is studied th eoretically and experimentally. The experiment is carried out with the use of the wide-band photoacoustic spectroscopy based on the laser excitation o f ultrasound and a wide-band signal detection. The fact that the transmissi on spectrum of a periodic structure has alternating pass and stop bands is confirmed experimentally. The width and localization of the stop bands stro ngly depend on the thickness of the layers and on the phase velocity of ult rasound in them. It is demonstrated that defects of the structure periodici ty give rise to one or several local transmission maxima in the stop band a nd to a modification of the pass band. The amplitude and position of a loca l maximum in the stop band strongly depend on the position of the defective layer. The experimental data agree well with the results of numerical simu lation. (C) 2000 MAIK "Nauka/Interperiodica".