Near field analysis for periodic diffractive gratings using Fourier modal method

Laser induced damage is a big problem for diffractive gratings used under high power laser condition. Beam modulation caused by fine structure of diffractive gratings has close relations with the risk of laser induced damage. In this paper, Fourier modal method is introduced to rapidly and accurately calculate the near field electromagnetic distribution of periodic diffractive gratings under high power condition. Through theoretically analysis and numerical calculation, amplitude and phase distributions of electric field are given both inside and outside the grating region, and the maximum amplitude modulation in near field region is also derived. Analytical calculation and numerical simulation results show that the electric field modulation strongly depends on the structure of grating groove, particularly grating period, groove depth and duty cycle. (c) 2006 Elsevier B.V. All rights reserved.