Maxwell + TDDFT multi-scale simulation for laser-matter interactions

We are developing a theoretical and computational method to describe interactions between an intense laser pulse and a solid. The laser-solid interactions are extensively investigated in current frontiers of optical sciences. There are two spatial scales in the problem: the scale of laser wavelength typically a μm and the scale of electron dynamics in a solid less than a nm. We have developed a multi-scale simulation for this problem, describing propagation of the electromagnetic fields by the Maxwell equations and the electron dynamics in a unit cell of a solid by the time-dependent density functional theory. In calculating the coupled dynamics, we employ a finite difference scheme for both space and time variables. Two kinds of grids with different grid spacings are used for space, while a single time step is used for time. We present our theoretical framework, numerical implementation, and parallelization of our multi-scale simulation. It will be shown that high parallel efficiency and computing performance are realized in our computational code.