Control of optical properties of silica glass synthesized by VAD method for photonic components

High-purity silica glass (SiO2) synthesized by vapor-phase methods has been extensively used as optical material for photolithography due to its high transmittance in the UV range. Furthermore, low birefringence is an essential property in order to attain distortion-free images of fine IC patterns. This research reports the development of low birefringence silica glass for photonic components that excludes the annealing requirement by controlling the processing parameters of the VAD (Vapor-phase Axial Deposition) method. Nanoparticles size radial homogeneity of silica soot boules was characterized by scanning electron microscopy (SEM). It was established a relationship with the birefringence of consolidated boules characterized through polarization spectrophotometry. As the most interesting results, low birefringence silica glass (<= 2 nm/cm) was synthesized with reduced fabrication time and cost besides simple processing stages by controlling the silica boule bottom shape during deposition processing in correlation with the consolidation time. (C) 2011 Elsevier B.V. All rights reserved.