Dependence of birefringence and residual stress near laser-induced cracks in fused silica on laser fluence and on laser-pulse number
- University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States)
Measurements of birefringence induced in fused-silica specimens by a crack produced by a 351-nm/500-ps Nd:glass laser as a function of laser fluence F{sub L} and of number of laser shots {ital N} are presented. The varying dimensional parameter is found to be the crack depth {ital a} and can be put in the form a(mm)=(0.0096{plus_minus}0.0021)N[(F{sub L}/F{sub exit/th}){minus}1]{sup 2/3} with F{sub L}{ge}F{sub exit/th}(F{sub exit/th} is the exit-surface damage threshold). The retardance data are converted into units of stress, thus permitting the estimation of residual stress near the crack. The results of the measured residual stress can be cast in the form {sigma}{sub r}(MPa){approx}(0.0386{plus_minus}0.0051)[(F{sub L}/F{sub exit/th}){minus}1]{sup 1/2}N{sup 2/3} with F{sub L}{ge}F{sub exit/th}. A theoretical model giving the stress field around a crack is developed for comparison and shows reasonable agreement with the experiment. Good agreement with experimental data of others is also obtained. The effect of residual stresses on fracture strength is pointed out. The results obtained show that the presence of birefringence/residual stress in a fused-silica specimen with a crack on its surface has a strong effect on fracture and should be taken into account in any formulation that involves the failure strength of optical components used in inertial-confinement-fusion experiments. {copyright} 1998 Optical Society of America
- Research Organization:
- Univ. of Rochester, NY (United States)
- DOE Contract Number:
- FC03-92SF19460
- OSTI ID:
- 295493
- Journal Information:
- Applied Optics, Vol. 37, Issue 33; Other Information: PBD: Nov 1998
- Country of Publication:
- United States
- Language:
- English
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