Finite-Difference Time-Domain Simulation of Strong-Field Ionization: A Perfectly Matched Layer Approach

A finite-difference time-domain (FDTD) scheme with perfectly matched layers (PMLs) is considered for solving the time-dependent Schrödinger equation and simulating the laser-induced ionization of two systems: 1) an electron initially bound to a 1D δ potential and 2) excitons in carbon nanotubes (CNTs). The performance of PMLs based on different absorption functions is compared, where slowly growing functions are found to be preferable. PMLs are shown to be able to reduce the computational domain, and thus the required numerical resources, by several orders of magnitude. This is demonstrated by testing the proposed method against an FDTD approach without PMLs and a very large computational domain. It is shown that PMLs outperform the well-known exterior complex scaling (ECS) technique for short-range potentials when implemented in FDTD. For long-range potentials such as in CNTs, however, ECS performs better than PMLs when propagating over many periods.