Wet etch process is applied to expose the bulk damage sites in KDP crystals to the surface for the examination by scanning electron microscopy(SEM)and optical microscopy.The damage sites induced by 1064 nm laser consi...Wet etch process is applied to expose the bulk damage sites in KDP crystals to the surface for the examination by scanning electron microscopy(SEM)and optical microscopy.The damage sites induced by 1064 nm laser consist of three distinct regions:a core,an outer region of modified material,and some oriented cracks.Laser irradiated with 355 nm results in an increase of damage density,a decrease of core diameter and,rarely,occurrence of the crack.WavelengKey Laboratory of Materials for High Power Laser,Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences,Shanghai 201800th dependence of the damage feature suggests that a repulsive force exists among the adjacent plasmas,which prevents further expansion of plasma and decreases the size of plasma.The deposited energy absorbed by the smaller plasma may not be able to generate the crack.展开更多
The electronic structure and geometric distribution of phosphor replaced by sulfur in potassium dihydrogen phosphate （KDP） are investigated by first-principles calculations. The point defect narrows down the energy ...The electronic structure and geometric distribution of phosphor replaced by sulfur in potassium dihydrogen phosphate （KDP） are investigated by first-principles calculations. The point defect narrows down the energy gap to about 4.9eV, corresponding to a two-photon absorption of 355nm after correction. This can explain the decrease of the laser damage resistance in KDP crystals. Moreover, the defects twist the crystal structure and weaken bonds, especially the O-H bonds, so these bonds may be the first sites to crack under laser irradiation.展开更多
Three kinds of KH2PO4 raw material are used to grow deuterated potassium dihydrogen phosphate （DKDP） crystals by traditional and rapid growth methods, respectively. The growth habit dependence on the purity of raw m...Three kinds of KH2PO4 raw material are used to grow deuterated potassium dihydrogen phosphate （DKDP） crystals by traditional and rapid growth methods, respectively. The growth habit dependence on the purity of raw material is described and analyzed. The optical properties including transmission spectra and laser-induced damage threshold of these crystals are measured. It is found that the growth method affects the optical properties of crystal more obviously than the raw material with the mass content of main metal ions below 1 ppm. Moreover, the morphology of the core in the observed damage sites indicates that an explosion process probably occurs during laser-induced breakdown.展开更多
The multilayer(ML)YSZ/SiO_(2) films with different modulation ratios ranging from 1:3,4:9,1:1 to 3:1(the thickness ratio of the YSZ to SiO_(2))are deposited on BK7 glass substrates by electron beam evaporation under t...The multilayer(ML)YSZ/SiO_(2) films with different modulation ratios ranging from 1:3,4:9,1:1 to 3:1(the thickness ratio of the YSZ to SiO_(2))are deposited on BK7 glass substrates by electron beam evaporation under the same processing conditions.The effect of modulation ratio on the residual stresses and structure are investigated by an optical interferometer and Grazing incidence x-ray diffraction.The results show that the total residual stress in MLs is compressive and decreases to tensile when the modulation ratio is changed from 1:3 to 3:1.The YSZ films are of cubic phase structure and the SiO_(2) films are amorphous in all the MLs.The change of residual stress in these MLs can be attributed to the variation of an individual layer?s stress with thickness,which indicates that adjusting the thickness ratio of two materials is an effective measure for depositing near-zero stress MLs.展开更多
A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate th...A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.展开更多
Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 10...Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C,the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased.After annealing in air at 500°C,the transmittance significantly increased and approached that of uncoated fused quartz.Based on the Tauc plot method and Mott-Davis-Paracrystalline model,the optical band gap of Ge films was calculated and interpreted.The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing,while having little effect on the optical band gap after annealing.Furthermore,due to oxidation of Ge films,the optical band gap was significantly increased to^5.7 eV after annealing.展开更多
The inclusions in conventionally grown KD2PO4 （DKDP） crystals are investigated. The inclusions are captured by a light-scattering technique. The sizes are determined by an optical microscope and a transmission elect...The inclusions in conventionally grown KD2PO4 （DKDP） crystals are investigated. The inclusions are captured by a light-scattering technique. The sizes are determined by an optical microscope and a transmission electron microscope （TEM）, and the compositions are analyzed by time of flight secondary ion mass spectrometry （TOF-SIMS） and an energy dispersive spectrometer （EDS）. Two kinds of inclusions are observed in the DKDP crystals： a submicron-scale inclusion and a micron-scale inclusion. The typical submicron-scale inclusions contain growth solution, and their sizes range from tens to hundreds of nanometers, whereas the micron-scale inclusions contain growth solution and the metal element Na, and the sizes are tens of microns. The possible formation mechanisms of the inclusions are discussed, and the influence of the inclusions on laser-induced damage behaviors are analyzed and discussed.展开更多
The spatial resolved method, which measures the laser-induced damage fluence by identifying the location of the damage point in the Gaussian beam three-dimensional direction, is demonstrated. The advantages and practi...The spatial resolved method, which measures the laser-induced damage fluence by identifying the location of the damage point in the Gaussian beam three-dimensional direction, is demonstrated. The advantages and practicality of this method have been explained. Taking a triple frequency beam splitter as an example, the defect damage fluence can be accurately calculated by the spatial resolved method. The different defect damage performance of the triple frequency splitter is distinguished under irradiations of only the 355 and 532 nm lasers. The spatial resolved method provides a way to obtain precise information of optical film defect information.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 60878045.
文摘Wet etch process is applied to expose the bulk damage sites in KDP crystals to the surface for the examination by scanning electron microscopy(SEM)and optical microscopy.The damage sites induced by 1064 nm laser consist of three distinct regions:a core,an outer region of modified material,and some oriented cracks.Laser irradiated with 355 nm results in an increase of damage density,a decrease of core diameter and,rarely,occurrence of the crack.WavelengKey Laboratory of Materials for High Power Laser,Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences,Shanghai 201800th dependence of the damage feature suggests that a repulsive force exists among the adjacent plasmas,which prevents further expansion of plasma and decreases the size of plasma.The deposited energy absorbed by the smaller plasma may not be able to generate the crack.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10676019 and 50721002, the Program for New Century Excellent Talents in University （NCET-10-0526）, and the Natural Science Foundation of Shandong Province （ZR2009FM015）.
文摘The electronic structure and geometric distribution of phosphor replaced by sulfur in potassium dihydrogen phosphate （KDP） are investigated by first-principles calculations. The point defect narrows down the energy gap to about 4.9eV, corresponding to a two-photon absorption of 355nm after correction. This can explain the decrease of the laser damage resistance in KDP crystals. Moreover, the defects twist the crystal structure and weaken bonds, especially the O-H bonds, so these bonds may be the first sites to crack under laser irradiation.
基金supported by the Program for New Century Excellent Talents in University(No.NCET-10-0526)the National Science Foundation of China(No.51323002)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2010EM001)the Independent Innovation Foundation of Shandong University(No.IIFSDU,2012JC016)
文摘Three kinds of KH2PO4 raw material are used to grow deuterated potassium dihydrogen phosphate （DKDP） crystals by traditional and rapid growth methods, respectively. The growth habit dependence on the purity of raw material is described and analyzed. The optical properties including transmission spectra and laser-induced damage threshold of these crystals are measured. It is found that the growth method affects the optical properties of crystal more obviously than the raw material with the mass content of main metal ions below 1 ppm. Moreover, the morphology of the core in the observed damage sites indicates that an explosion process probably occurs during laser-induced breakdown.
基金Supported by the National Natural Science Foundation of China under Grant No 10976030.
文摘The multilayer(ML)YSZ/SiO_(2) films with different modulation ratios ranging from 1:3,4:9,1:1 to 3:1(the thickness ratio of the YSZ to SiO_(2))are deposited on BK7 glass substrates by electron beam evaporation under the same processing conditions.The effect of modulation ratio on the residual stresses and structure are investigated by an optical interferometer and Grazing incidence x-ray diffraction.The results show that the total residual stress in MLs is compressive and decreases to tensile when the modulation ratio is changed from 1:3 to 3:1.The YSZ films are of cubic phase structure and the SiO_(2) films are amorphous in all the MLs.The change of residual stress in these MLs can be attributed to the variation of an individual layer?s stress with thickness,which indicates that adjusting the thickness ratio of two materials is an effective measure for depositing near-zero stress MLs.
基金supported by the National Key Research and Development Project of China(No.2016YFE0104300)
文摘A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.
基金supported by the National Key Research and Development Project of China (No. 2016YFE0104300)
文摘Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C,the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased.After annealing in air at 500°C,the transmittance significantly increased and approached that of uncoated fused quartz.Based on the Tauc plot method and Mott-Davis-Paracrystalline model,the optical band gap of Ge films was calculated and interpreted.The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing,while having little effect on the optical band gap after annealing.Furthermore,due to oxidation of Ge films,the optical band gap was significantly increased to^5.7 eV after annealing.
基金supported by the National Natural Science Foundation of China under Grant 61405219
文摘The inclusions in conventionally grown KD2PO4 （DKDP） crystals are investigated. The inclusions are captured by a light-scattering technique. The sizes are determined by an optical microscope and a transmission electron microscope （TEM）, and the compositions are analyzed by time of flight secondary ion mass spectrometry （TOF-SIMS） and an energy dispersive spectrometer （EDS）. Two kinds of inclusions are observed in the DKDP crystals： a submicron-scale inclusion and a micron-scale inclusion. The typical submicron-scale inclusions contain growth solution, and their sizes range from tens to hundreds of nanometers, whereas the micron-scale inclusions contain growth solution and the metal element Na, and the sizes are tens of microns. The possible formation mechanisms of the inclusions are discussed, and the influence of the inclusions on laser-induced damage behaviors are analyzed and discussed.
基金supported by the National Natural Science Foundation of China(No.4317)the National Key Research and Development Project of China(No.2016YFE0104300)
文摘The spatial resolved method, which measures the laser-induced damage fluence by identifying the location of the damage point in the Gaussian beam three-dimensional direction, is demonstrated. The advantages and practicality of this method have been explained. Taking a triple frequency beam splitter as an example, the defect damage fluence can be accurately calculated by the spatial resolved method. The different defect damage performance of the triple frequency splitter is distinguished under irradiations of only the 355 and 532 nm lasers. The spatial resolved method provides a way to obtain precise information of optical film defect information.
