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...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 IEImax is 18.57314 V/m. When θ ranges from π/θ 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.展开更多
Dry laser cleaning(DLC)and laser shockwave cleaning(LSC)are used to remove the particulate contamination from SiO_(2) sol−gel optical films.The results show that the LSC with a shockwave initiated by plasma formation ...Dry laser cleaning(DLC)and laser shockwave cleaning(LSC)are used to remove the particulate contamination from SiO_(2) sol−gel optical films.The results show that the LSC with a shockwave initiated by plasma formation under a focused laser beam pulse offers much better efficiency than DLC.Silica particles up to 10µm on SiO_(2 )films can be removed without substrate damage at a gap distance of 0.5 mm,and a more uniform surface microstructure can be obtained after LSC.Furthermore,it is demonstrated that the transmittance of contaminated SiO2 films can be restored to the as-deposited value after the LSC on dispersed-particle zones.LSC has potential applications in engineering-oriented large components.展开更多
Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning...Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning electron microscopy show that the lattice distortions of the PbWO4 microcrystals are reduced significantly when the annealing temperature is increased to 873 K. The result from the ultraviolet-visible diffuse reflectance spectroscopy shows that the exciton absorption appears in the sample annealed at 673 K. The self-trapped exciton luminescence due to the Jahn- Teller effect is also observed in the blue band. The interstitial oxygen ions in the WO42- groups are mainly resposible for the enhancement effect of the green luminescence of the annealed samples. The above results are supported by the spectrum analysis of the as-grown and the post-annealed samples using the X-ray photoelectron spectroscopy.展开更多
Density functional molecular dynamics are used to study the melting behavior of single-walled SiC nanotubes. The melting of SiC nanotubes starts from the thermally activated Stone—Wales defects. The melting temperatu...Density functional molecular dynamics are used to study the melting behavior of single-walled SiC nanotubes. The melting of SiC nanotubes starts from the thermally activated Stone—Wales defects. The melting temperature is found to increase with the increasing diameter of nanotubes. The SiC nanotubes have a high melting temperature larger than 4000 K as the diameter larger than 1.0 nm, which indicates that the SiC nanotubes may be the best candidate of nanoscale electronic and optoelectronic devices under high temperatures.展开更多
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No.10904008)the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (GrantNo. 11076008)the Scientific Research Foundation for the Central Universities of China (Grant Nos.ZYGX2009X007,ZYGX2010J045, and ZYGX2011J043)
文摘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 IEImax is 18.57314 V/m. When θ ranges from π/θ 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.
基金by the National High-Technology Research and Development Program of China(2008AA8040508)the Funda-mental Research Funds for the Central Universities(ZYGX2009X007).
文摘Dry laser cleaning(DLC)and laser shockwave cleaning(LSC)are used to remove the particulate contamination from SiO_(2) sol−gel optical films.The results show that the LSC with a shockwave initiated by plasma formation under a focused laser beam pulse offers much better efficiency than DLC.Silica particles up to 10µm on SiO_(2 )films can be removed without substrate damage at a gap distance of 0.5 mm,and a more uniform surface microstructure can be obtained after LSC.Furthermore,it is demonstrated that the transmittance of contaminated SiO2 films can be restored to the as-deposited value after the LSC on dispersed-particle zones.LSC has potential applications in engineering-oriented large components.
基金supported by the Fundamental Research Funds for the Central Universities,China(Grant Nos.ZYGX2009J046 and ZYGX2009X007)the Sichuan Provincial Young Scientists Foundation,China(Grant No.2010JQ0006)+1 种基金the Royal Society-Research Grant,UK(Grant No.RG090609)the Royal Academy of Engineering-Research Exchanges with China and India Awards in UK
文摘Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning electron microscopy show that the lattice distortions of the PbWO4 microcrystals are reduced significantly when the annealing temperature is increased to 873 K. The result from the ultraviolet-visible diffuse reflectance spectroscopy shows that the exciton absorption appears in the sample annealed at 673 K. The self-trapped exciton luminescence due to the Jahn- Teller effect is also observed in the blue band. The interstitial oxygen ions in the WO42- groups are mainly resposible for the enhancement effect of the green luminescence of the annealed samples. The above results are supported by the spectrum analysis of the as-grown and the post-annealed samples using the X-ray photoelectron spectroscopy.
基金Supported by the National Natural Science Foundation of China （10704014）, the Sichuan Young Scientists Foundation （09ZQ026-029）, and the PhD Funding Support Program of Education Ministry of China （20090450052）.
文摘Density functional molecular dynamics are used to study the melting behavior of single-walled SiC nanotubes. The melting of SiC nanotubes starts from the thermally activated Stone—Wales defects. The melting temperature is found to increase with the increasing diameter of nanotubes. The SiC nanotubes have a high melting temperature larger than 4000 K as the diameter larger than 1.0 nm, which indicates that the SiC nanotubes may be the best candidate of nanoscale electronic and optoelectronic devices under high temperatures.
