Analysis of the topography of a Bragg grating in chalcogenide glass

Relief Bragg gratings were recorded on the surface of Ga-Ge-S glass samples by interference of two UV laser beams at 351 nm, Scanning force microscopy was used to perform a 3D image analysis of the resulting surface topograph y, which shows the superposition of an imprinted grating over the base topo graphy of the glass. An important question regarding the efficiency of the grating is to determine to what extent the base topography reduces the inte nded coherent scattering of the grating because of its stochastic character . To answer this question we separated both base and grating structures by Fourier filtering, examined both spatial frequency and roughness, and deter mined the correlation. (C) 2001 Elsevier Science B.V. All rights reserved.