A Basic Complete Numerical Toolbox for Picosecond Ultrasonics

Abstract

A complete numerical complete toolbox is proposed concerning the simulation of photo-induced propagative mechanical wave, and concerning the optical reflectometric measured response of the material, which is initially exposed to a first pump laser beam that photo-induces the acoustic wavefronts. The deformation field and its propagation into a bulk material are simulated. Based on this field expression, the complex transient reflectivity is given for a medium considered as homogeneous. The real part of this quantity permits afterwards to propose a numerical simulation of the transient reflectivity, which corresponds to the optical signal measured during experimental works. The frequency acoustic spectrum is simulated and successfully compared to the measured frequency spectrum. For the first time, numerical complete developments are explicitly proposed and fully-developed under the SciLab ® environment, related to the simulation of laser-induced picosecond acoustic wavefront photogenerated through an opto-acoustic transduction process (ultrasonics and pretersonics).

Simulation of multiwavelength conditions in laser picosecond ultrasonics

“…The most favorable optical configuration for optical probing of photo-induced propagative acoustic modes seem to be (for the GaAs material considered in the present study) the red-red and the red-blue pump-probe configurations, corresponding to a volumic large excitation and a large or surface detection. 56 Figures 6-9 are relevant to the calculations and estimations given by authors in the literature, 57 given that ∂n ∂h l = 400 nm ð Þffi20 3 ∂n ∂h l = 800 nm ð Þ , which indicates Laser configuration given in the insert. The interface between air and substrate is located at 0 nm.…”