Finite-Difference Time Domain Analysis of Ultrashort Pulse Laser Light Propagation under Nonlinear Coupling

Abstract

Aim of this study is to propose a numerical model and to calculate ultrashort pulse laser light propagation by using Finite-Difference Time Domain (FDTD). “Ultrashort” pulse here is defined so that the Slowly Varying Envelope Approximation (SVEA) breaks in Beam Propagation Method (BPM) and corresponds to the pulse width of typically several tens of femtoseconds or shorter. In this case, FDTD must be used instead of BPM. In our FDTD-based model, nonlinear absorption and the effect of laser-induced plasma are newly considered unlike previously reported FDTD models. In this paper, we examine the results of FDTD-based calculation by comparing with the results of BPM-based calculation in short pulse cases where the SVEA approximation is valid. Furthermore, we calculate ultrashort pulse laser propagation and the results can describe the essential features in ultrahigh power regime.

Keywords

• nonlinear optical effect
• ultrashort pulse laser
• finite difference time domain
• simulation of laser nanomachining