Use of Abcd-Matrix Method For The Simulation of Laser-Ultrasonic Probing Pulse Propagation In A Layered Medium of The Optical-Acoustic Transducer

Abstract

As a first step methods for modeling the propagation of acoustic waves in layered media was analyzed and the need to develop a new, faster method is substantiated. As a consequence, presented a method for modeling the propagation of elastic waves based on signal transformation using ABCD matrices, for the implementation of which a computer program in the Python language has been developed. For the verification of the method was analyzed the correlation between the simulated signal and the signal obtained experimentally from a medium with predetermined parameters. Further on the basis of the data obtained, the applicability of this method for modeling the propagation of acoustic signals in a plane-layered medium has been proved. As a next step modern methods of ultrasound generation and their influence on the characteristics of the probing signal was reviewed. Confirmed that laser-ultrasound techniques allow the best control over the characteristics of the probe signal. Therefore, the influence of the duration of the laser pulse, the properties of light absorption and the acoustic characteristics of the generator medium on the probing signal amplitude and bandwidth of the spectrum was estimated. To reduce the influence of the considered characteristics on the diagnostic process using the ABCD-matrix method the optimal characteristics of the optical-acoustic transducer for diagnostics at low frequencies have been determined. Finally, the main advantage of the proposed modeling method is the high speed of calculating the shape and spectrum of the signal at any point in the medium at a given time.