Simulations of photoacoustic wave propagation using a finite-difference time-domain method with Berenger's perfectly matched layers

Abstract

This study developed a numerical solution of the general photoacoustic generation equations involving the heat conduction theory and the state, continuity, and Navier-Stokes equations in 2.5D axisymmetric cylindrical coordinates using a finite-difference time-domain scheme. The numerical techniques included staggered grids and Berenger's perfectly matched layers (PMLs), and linear-perturbation analytical solutions were used to validate the simulation results. The numerical results at different detection angles and durations of laser pulses agreed with the theoretical estimates to within an error of 2% in the absolute differences. It was also demonstrated that the simulator can be used to develop advanced photoacoustic imaging methods. The performance of Berenger's PMLs was also assessed by comparisons with the traditional first-order Mur's boundary condition. At the edges of the simulation domain, a ten-layer PML medium with polynomial attenuation coefficient grading from 0 to 5 x 10(6) m(3)/kg s was designed to reduce the reflection to as low as -60 and -32 dB in the axial and radial directions, respectively. The reflections at the axial and radial boundaries were 32 and 7 dB lower, respectively, for the ten-layer PML absorbing layer than for the first-order Mur's boundary condition.