摘要
A non-evaporative technique is used to mitigate damage sites with lateral sizes in a range from 50 μm to 400 μm and depths smaller than 100 μm.The influence of the pulse frequency of a CO 2 laser on the mitigation effect is studied.It is found that a more symmetrical and smooth mitigation crater can be obtained by increasing the laser pulse frequency form 0.1 to 20 kHz.Furthermore,the sizes of laser-affected and distorted zones decrease with the increase of the laser pulse frequency,leading to less degradation of the wave-front quality of the conditioned sample.The energy density of the CO 2 laser beam is introduced for selecting the mitigation parameters.The damage sites can be successfully mitigated by increasing the energy density in a ramped way.Finally,the laser-induced damage threshold（LIDT） of the mitigated site is tested using 355 nm laser beam with a small spot（0.23 mm 2） and a large spot（3.14 mm 2）,separately.It is shown that the non-evaporative mitigation technique is a successful method to stop damage re-initiation since the average LIDTs of mitigated sites tested with small or large laser spots are higher than that of pristine material.
A non-evaporative technique is used to mitigate damage sites with lateral sizes in a range from 50 μm to 400 μm and depths smaller than 100 μm.The influence of the pulse frequency of a CO 2 laser on the mitigation effect is studied.It is found that a more symmetrical and smooth mitigation crater can be obtained by increasing the laser pulse frequency form 0.1 to 20 kHz.Furthermore,the sizes of laser-affected and distorted zones decrease with the increase of the laser pulse frequency,leading to less degradation of the wave-front quality of the conditioned sample.The energy density of the CO 2 laser beam is introduced for selecting the mitigation parameters.The damage sites can be successfully mitigated by increasing the energy density in a ramped way.Finally,the laser-induced damage threshold（LIDT） of the mitigated site is tested using 355 nm laser beam with a small spot（0.23 mm 2） and a large spot（3.14 mm 2）,separately.It is shown that the non-evaporative mitigation technique is a successful method to stop damage re-initiation since the average LIDTs of mitigated sites tested with small or large laser spots are higher than that of pristine material.
基金
Project supported by the National High Technology Research and Development Program of China(Grant No.2008AA8040508)
Foundation for Young Scholars of University of Electronic Science and Technology of China(Grant No.L08010401JX0806)
the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics(Grant No.11076008)
the Fundamental Research Funds for the Central Universities of China(Grant No.ZYGX2011J043)
the Sichuan Provincial Young Scientists Foundation,China(Grant No.2010JQ0006)
