Rear-surface light intensification caused by a Hertzian-conical crack in 355-nm silica optics |
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Authors: | Zhang Chun-Lai Yuan Xiao-Dong Xiang Xia Wang Zhi-Guo Liu Chun-Ming Li Li He Shao-Bo and Zu Xiao-Tao |
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Institution: | [1]School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 6]0054, China [2]Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China |
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Abstract: | Theoretical studies show that a Hertzian-conical crack can be considered to be composed of double cone faces for simplicity. In the present study, the three-dimensional finite-difference time-domain method is employed to quantify the electric-field distribution within the subsurface in the presence of such a defect under normal incidence irradiation. Both impurities (inside the crack) and the chemical etching have been investigated. The results show that the maximum electric field amplitude |E| max is 9.57374 V/m when the relative dielectric constant of transparent impurity equals 8.5. And the near-field modulation will be improved if the crack is filled with the remainder polishing powders or water vapor/drops. Meanwhile, the laser-induced initial damage moves to the glass–air surface. In the etched section, the magnitude of intensification is strongly dependent on the inclination angle θ. There will be a highest modulation when θ is around π/6, and the maximum value of |E| max is 18.57314 V/m. When θ ranges from π/8 to π/4, the light intensity enhancement factor can easily be larger than 100, and the modulation follows a decreasing trend. On the other hand, the modulation curves become smooth when θ > π/4 or θ < π/8. |
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Keywords: | fused silica wet etching Hertzian-conical crack finite-difference time-domain method |
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