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Advances in Condensed Matter Physics
Volume 2014, Article ID 638045, 5 pages
http://dx.doi.org/10.1155/2014/638045
Research Article

Investigation of Control of Residual Stress Induced by CO2 Laser-Based Damage Mitigation of Fused Silica Optics

Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China

Received 27 February 2014; Accepted 11 May 2014; Published 3 June 2014

Academic Editor: Haiyan Xiao

Copyright © 2014 Chuanchao Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A CO2 laser-based annealing technique for the mitigation of damaged sites of fused silica is studied to suppress the residual stress left on the surface. The laser annealing by a linear decrease of the CO2 laser power effectively reduces the residual stress. The residual stress of mitigated sites is characterized by polarimetry, the reduction of the maximum retardance around the mitigated sites with the exposure time of laser annealing fits a stretched exponential equation, and the maximum retardance with optimal laser annealing is reduced (36 ± 3)% compared to that without laser annealing. The residual stress regions are destructively characterized by introducing damage. The critical size of damage leading to fracture propagation for the mitigated sites without laser annealing is in the range of 120~230 μm, and the corresponding critical size of damage for the mitigated sites with laser annealing is larger than 600 μm. According to the relationship between maximum damage size and critical stress, the residual stress without laser annealing is in the range of 28–39 MPa and the residual stress with laser annealing is less than 17 MPa. These results indicate that the CO2 laser-based annealing technique has a positive effect on the control of residual stress induced by CO2 laser-based damage mitigation.