Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and ch...Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and characterized by ultraviolet-visual (UV), fourier transform infrared (FIF-IR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The experimental results of UV, FT-IR and XPS show that the Tb (III)-PNVA electrovalent complex is formed by electrostatic interaction between terbium (III) cation and complexible atoms of acylamino group in the pendant chain of the polymer. The fluorescence spectrum of the complex exhibits intensive characteristic emission of terbium at 490, 545 and 584 run, which are assigned to D-5(4)->F-7(6), D-5(6)->F-5(6) and D-5(4)->F-7(3) transition, indicating that there exists an efficient intermolecular energy transfer from the polymer ligand to the central rare earth ion. The emission intensity of the complex is increased with the increasing concentration of Tb (III) ion until the weight ratio of Tb (III) on to PNVA is 1.5% (mass fraction), and decreased with the further increasing concentration of Tb (III) ion, which is a typical concentration quenching behavior.展开更多
The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing ...The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing machine. Compared with unmodified Al-10 Si alloy, the area fraction of α-Al phase in Al-10 Si alloy modified at 740 °C increased first and then decreased with the increase of added amounts of Al-5 Ti, and reached the maximum when the added amount of Al-5 Ti was 0.5 wt.%. When the modification temperature increased from 700 to 740 °C with Al-5 Ti being fixed at 0.5 wt.%, α-Al dendrites were refined obviously and the area fraction remarkably increased. Compared with unmodified Al-10 Si alloy, the ultimate tensile strength and elongation of the alloy modified at 740 °C with 0.5 wt.% Al-5 Ti increased by 9% and 49%, respectively. The fracture surface of modified alloy predominantly exhibited ductile fracture.展开更多
The tensile properties of 2297-T87 Al–Li alloy thick plates at different thickness position and in different direction were analyzed via tensile testing,optical microscopy(OM),X-ray diffraction(XRD),scanning electron...The tensile properties of 2297-T87 Al–Li alloy thick plates at different thickness position and in different direction were analyzed via tensile testing,optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).Results indicated that the ultimate tensile strength(UTS)and yield strength(YS)of the alloy decreased firstly and then increased from the 1/8T position to the 1/2T position,whereas elongation to failure(Ef)decreased gradually such that its value along the rolling direction(RD)was higher than those along the transverse direction(TD)at the same thickness position.From the 1/8T position to the 3/8T position of the alloy,the UTS and YS along the TD were higher than those along the RD.At the 1/2T position of the alloy,the UTS,YS,and Ef along the RD were the highest,whereas those along the normal direction(ND)were the lowest.Microstructural observations further revealed that the anisotropy of tensile properties was related to grain morphology,crystal texture,second-phase particles,and Li atom segregation.展开更多
Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resona...Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained.展开更多
Al-Si alloy was modified with Al-3P master alloy at 740℃.The effects of Si content(7,8,9,10 and 11 wt.%) and adding amount of alterant A1-3P(0,0.1,0.3,0.6,1.0 and 1.5 wt.%) on microstructures and tensile properties o...Al-Si alloy was modified with Al-3P master alloy at 740℃.The effects of Si content(7,8,9,10 and 11 wt.%) and adding amount of alterant A1-3P(0,0.1,0.3,0.6,1.0 and 1.5 wt.%) on microstructures and tensile properties of the alloy were investigated with optical microscope(OP),Image Pro Plus 6.0,scanning electron microscope(SEM) and universal testing machine.When the content of Al-3P is 0.6 wt.%,the area fraction of primary a(Al) in the Al-Si alloy increases more compared to the unmodified alloy with an increase in Si content,which could be explained by the movement of non-equilibrium eutectic point.When the Si content is constant(Al-lOSi),with the increase of Al-3P content,the increased rate in area fraction of primary a(Al) phase in the Al-lOSi alloy increases first and then decreases.And when 0.6 wt.% Al-3P is added,the increase in area fraction of primary a(Al) phase is the largest.Compared to the unmodified Al-lOSi alloy,the tensile strength and elongation of Al-lOSi alloy increase by 2.3% and 47.0%,respectively,after being modified with 0.6 wt.% Al-3P alloy.The fracture mode of the modified Al-lOSi alloy is ductile fracture.展开更多
We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection co...We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection coating with a quintic effective refractive-index profile for a given state of polarization has been discussed. In addition, the genetic algorithm was used to optimize the refractive index profile of the GRIN antireflection for reducing the mean reflectance of s- and p-polarizations. The average reflectance loss was reduced to only 0.04% by applying optimized GRIN AR coatings onto BK7 glass over the wavelength range from 400 to 800 nm at the incident angle of θo = 70°.展开更多
In the comparison of damage modifications, absorption measurement and energy dispersive x-ray analysis, the effect of vacuum on the laser-induced damage of anti-reflection coatings is analyzed. It is found that vacuum...In the comparison of damage modifications, absorption measurement and energy dispersive x-ray analysis, the effect of vacuum on the laser-induced damage of anti-reflection coatings is analyzed. It is found that vacuum decreases the laser-induced damage threshold of the films. The low laser-induced damage threshold in vacuum environments as opposed to air environments is attributed to water absorption and the formation of the O/Si, O/Zr sub-stoichiometry in the course of laser irradiation.展开更多
The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflectio...The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflection band with the distribution of the periods are investigated.The improvement of the steepness of the stopband edges and the suppression of the side lobes in the transmission zone are realized by adding two apodized rugate structures with fixed periods at the external broadband rugate filter interfaces.The rapidly alternating deposition technology is used to fabricate a rugate filter sample.The measured transmission spectrum with a reflection bandwidth of approximately 505 nm is close to that of the designed broadband rugate filter except a transmittance peak in the stopband.Based on the analysis of the cross-sectional scanning electron microscopic image of the sample,it is found that the transmission peak is most likely to be caused by the instability of the deposition rate.展开更多
We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were de...We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were deposited on nitrided sapphire, low-temperature InN （LT-InN） and high-temperature GaN （HT-GaN）, respectively. The InN layer grown directly on nitrided sapphire owns the narrowest x-ray diffraction rocking curve （XRC） width of 300 aresee among the three samples, and demonstrates a two-dimensional （2D） step-flow-like lateral growth mode, which is much different from the three-dimensional （3D） pillar-like growth mode of LT-InN and HT-GaN buffered samples. It seems that mismatch tensile strain is helpful for the lateral epitaxy of InN film, whereas compressive strain promotes the vertical growth of InN films.展开更多
In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mo...In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phe- nomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and -lst transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in -lst transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented.展开更多
Laser damage performance of multilayer films with combined irradiation of 1ω and 2ω is studied to probe the damage mechanisms during wavelength division. The laser induced damage thresholds （LIDTs） of the samples ...Laser damage performance of multilayer films with combined irradiation of 1ω and 2ω is studied to probe the damage mechanisms during wavelength division. The laser induced damage thresholds （LIDTs） of the samples are obtained and tested with only 2ω with various energy densities of 1ω. Different 1ω; polarization directions combined with the 2ω case are also investigated. The result suggests that lw can raise the damage probability of multilayer mirrors when two light wavelengths are present simultaneously; the increasing number of sensitive defects for 2ω can be related to the decline of the LIDTs of the multilayer mirrors.展开更多
The interface structure and electronic properties of Fe(110)/Al(110) are investigated by the first-principles plane-wave pseudopotential method. The interface segregation position of Si and Mg is determined, and the e...The interface structure and electronic properties of Fe(110)/Al(110) are investigated by the first-principles plane-wave pseudopotential method. The interface segregation position of Si and Mg is determined, and the effect of Mg and Si on the interface binding of Fe(110)/Al(110) is analyzed by combining the work of separation and charge density. The results show that the Fe(110)/Al(110) interface energy of FeHollow coordination is smaller and the interface structure is more stable. The Fe(110)/Al(110) interface separation surface in the form of Fe-Hollow coordination appears at the sub interface layer on the side of Al(110)near the interface. The interface structure of Mg and Si segregation is similar to that of undoped alloy elements.The calculations also suggest that Mg and Si segregate on the Al(110) side of the interface and occupy the Al lattice on the Al(110) side. The segregation of Mg and Si elements will reduce the interface binding, primarily because the Fe-Si bond and Fe-Mg bond are weaker than Fe-Al bond.展开更多
By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is pro...By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is proved that laser conditioning is an efficient way to improve the damage resistance. The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps. We have also found that the damage resistance of the z-cut crystal is higher than the triplet cut, and the pinpoint number is definitely less in the z-cut crystal. The reason for these observations is discussed.展开更多
A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating dep...A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technol- ogy. The optical properties of the composite films varying with the composition of the material are studied in detail, Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a re- flection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra axe in good agreement with each other, The causes of the slight differences between them are also analysed.展开更多
The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a geneti...The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.展开更多
The evolution of stress in evaporated SiO2, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures （thin film deposit...The evolution of stress in evaporated SiO2, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures （thin film deposition, stopping deposition, cooling, venting the vacuum chamber, and exposing coated optics to the atmosphere） is put forward. Further investigations into the subprocedures reveal their features. During the deposition stage, the stresses are usually compressive and reach a stable state when the deposited film is thicker than 100 nm. An increment of compressive stress value is observed with the decrease of residual gas pressure or deposition rate. A very low stress of-20 MPa is formed in SiO2 films deposited at 3×10^-2 Pa. After deposition, the stress increases slightly in the compressive direction and is subject to the stabilization in subsequent tens of minutes. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours. An initial discussion of these behaviors is given.展开更多
YAG：Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique （TGT）. The effects of annealing on the luminescence efficiency of YAG：Ce crystal are investigated, and the optim...YAG：Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique （TGT）. The effects of annealing on the luminescence efficiency of YAG：Ce crystal are investigated, and the optimal annealing temperature and atmosphere are obtained. The mechanism of variation behavior of the luminescence efficiency of YAG：Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed.展开更多
The growth of a Mn-doped LiAlO_2 single crystal by the Czochralski（CZ） method and the characterization of its spectroscopy and thermoluminescence（TL） are presented.The X-ray rocking curve and chemical etching anal...The growth of a Mn-doped LiAlO_2 single crystal by the Czochralski（CZ） method and the characterization of its spectroscopy and thermoluminescence（TL） are presented.The X-ray rocking curve and chemical etching analysis show that the as-grown crystal has good crystallinity.The full-width at half-maximum （FWHM） of the LiAlO_2（200）ωrocking curve is 23.2 arcsec and the etching pits density of the（100） plane is（1.6-4.0）×10~4 cm^（-2）.The transmission spectrum indicates that the crystal is highly transparent in the 200-1500-nm wavelength range.The emission spectrum of the crystal consists of a peak around 579 nm when excited with 428-nm light.The TL spectra show that the LiAlO_2：Mn crystal has glow peaks at 150 and 172℃.The change of TL characteristics of the crystal before and after thermal annealing in the air is discussed,and the effect of annealing and irradiation on the evolution of defect types is analyzed.展开更多
The emission properties of 2-um region fluorescence of Tm^3＋-Ho^3＋ co-doped tellurite glasses are investigated. Introducing F- ions to the composition of tellurite glasses plays a positive effect on the 2-#m emissio...The emission properties of 2-um region fluorescence of Tm^3＋-Ho^3＋ co-doped tellurite glasses are investigated. Introducing F- ions to the composition of tellurite glasses plays a positive effect on the 2-#m emission. A maximum intensity of 2-um emission is achieved when 1.5-mol% Tm2O3 and 1-mol% Ho203 concentration are doped in the glasses. The emission cross section and gain coefficient of the ^5I8-^5I7 transition of Ho^3＋ are calculated. The emission cross section has a maximum of 1.29×10-20 cm^2 at 2048 nm wavelength. The results indicate that Tm＆3＋-Ho^3＋ co-doped tellurite glasses are suitable for 2-um application.展开更多
In contrast to uncoated substrate, a nonlinear relationship of phase shift with the thicknesses of the thin film makes the calculation of wavefront aberration complicated. A program is compiled to calculate the wavefr...In contrast to uncoated substrate, a nonlinear relationship of phase shift with the thicknesses of the thin film makes the calculation of wavefront aberration complicated. A program is compiled to calculate the wavefront aberration of multilayer thin film produced by thickness nonuniformity. The physical thickness and the optical phase change on reflection are considered. As an example, the wavefront aberration of the all-dielectric mirror is presented in ArF excimer lithography system with a typical thickness distribution. In addition, the wavefront errors of the thin film at wavelengths of 193 and 633 nm are compared in the one-piece and two-piece arrangements. Results show that the phase shift upon reflection of the thin film produced by thickness nonuniformity is very sensitive to the incident angle, wavelength, and polarization.展开更多
文摘Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and characterized by ultraviolet-visual (UV), fourier transform infrared (FIF-IR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The experimental results of UV, FT-IR and XPS show that the Tb (III)-PNVA electrovalent complex is formed by electrostatic interaction between terbium (III) cation and complexible atoms of acylamino group in the pendant chain of the polymer. The fluorescence spectrum of the complex exhibits intensive characteristic emission of terbium at 490, 545 and 584 run, which are assigned to D-5(4)->F-7(6), D-5(6)->F-5(6) and D-5(4)->F-7(3) transition, indicating that there exists an efficient intermolecular energy transfer from the polymer ligand to the central rare earth ion. The emission intensity of the complex is increased with the increasing concentration of Tb (III) ion until the weight ratio of Tb (III) on to PNVA is 1.5% (mass fraction), and decreased with the further increasing concentration of Tb (III) ion, which is a typical concentration quenching behavior.
基金financially supported by the National Natural Science Foundation of China(No.51571039)
文摘The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing machine. Compared with unmodified Al-10 Si alloy, the area fraction of α-Al phase in Al-10 Si alloy modified at 740 °C increased first and then decreased with the increase of added amounts of Al-5 Ti, and reached the maximum when the added amount of Al-5 Ti was 0.5 wt.%. When the modification temperature increased from 700 to 740 °C with Al-5 Ti being fixed at 0.5 wt.%, α-Al dendrites were refined obviously and the area fraction remarkably increased. Compared with unmodified Al-10 Si alloy, the ultimate tensile strength and elongation of the alloy modified at 740 °C with 0.5 wt.% Al-5 Ti increased by 9% and 49%, respectively. The fracture surface of modified alloy predominantly exhibited ductile fracture.
基金financially supported by the National Natural Science Foundation of China(Nos.52171029,51671038)the Major Natural Science Research Project of Higher Education Institutions in Jiangsu Province(No.18KJA430002)。
文摘The tensile properties of 2297-T87 Al–Li alloy thick plates at different thickness position and in different direction were analyzed via tensile testing,optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).Results indicated that the ultimate tensile strength(UTS)and yield strength(YS)of the alloy decreased firstly and then increased from the 1/8T position to the 1/2T position,whereas elongation to failure(Ef)decreased gradually such that its value along the rolling direction(RD)was higher than those along the transverse direction(TD)at the same thickness position.From the 1/8T position to the 3/8T position of the alloy,the UTS and YS along the TD were higher than those along the RD.At the 1/2T position of the alloy,the UTS,YS,and Ef along the RD were the highest,whereas those along the normal direction(ND)were the lowest.Microstructural observations further revealed that the anisotropy of tensile properties was related to grain morphology,crystal texture,second-phase particles,and Li atom segregation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)
文摘Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained.
基金Projects(51571039,51671037)supported by the National Natural Science Foundation of ChinaProject(KYCX18-0820)supported by Postgraduate Research and Practice Innovation Program of Jiangsu Province,ChinaProject supported by Qing Lan Program of Education Department of Jiangsu Province,China
文摘Al-Si alloy was modified with Al-3P master alloy at 740℃.The effects of Si content(7,8,9,10 and 11 wt.%) and adding amount of alterant A1-3P(0,0.1,0.3,0.6,1.0 and 1.5 wt.%) on microstructures and tensile properties of the alloy were investigated with optical microscope(OP),Image Pro Plus 6.0,scanning electron microscope(SEM) and universal testing machine.When the content of Al-3P is 0.6 wt.%,the area fraction of primary a(Al) in the Al-Si alloy increases more compared to the unmodified alloy with an increase in Si content,which could be explained by the movement of non-equilibrium eutectic point.When the Si content is constant(Al-lOSi),with the increase of Al-3P content,the increased rate in area fraction of primary a(Al) phase in the Al-lOSi alloy increases first and then decreases.And when 0.6 wt.% Al-3P is added,the increase in area fraction of primary a(Al) phase is the largest.Compared to the unmodified Al-lOSi alloy,the tensile strength and elongation of Al-lOSi alloy increase by 2.3% and 47.0%,respectively,after being modified with 0.6 wt.% Al-3P alloy.The fracture mode of the modified Al-lOSi alloy is ductile fracture.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10704079 and 10976030)
文摘We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection coating with a quintic effective refractive-index profile for a given state of polarization has been discussed. In addition, the genetic algorithm was used to optimize the refractive index profile of the GRIN antireflection for reducing the mean reflectance of s- and p-polarizations. The average reflectance loss was reduced to only 0.04% by applying optimized GRIN AR coatings onto BK7 glass over the wavelength range from 400 to 800 nm at the incident angle of θo = 70°.
基金Supported by the National Natural Science Foundation of China under Grant No 60708004.
文摘In the comparison of damage modifications, absorption measurement and energy dispersive x-ray analysis, the effect of vacuum on the laser-induced damage of anti-reflection coatings is analyzed. It is found that vacuum decreases the laser-induced damage threshold of the films. The low laser-induced damage threshold in vacuum environments as opposed to air environments is attributed to water absorption and the formation of the O/Si, O/Zr sub-stoichiometry in the course of laser irradiation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)the NSAF Joint Fund,China(Grant No. 10976030)
文摘The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflection band with the distribution of the periods are investigated.The improvement of the steepness of the stopband edges and the suppression of the side lobes in the transmission zone are realized by adding two apodized rugate structures with fixed periods at the external broadband rugate filter interfaces.The rapidly alternating deposition technology is used to fabricate a rugate filter sample.The measured transmission spectrum with a reflection bandwidth of approximately 505 nm is close to that of the designed broadband rugate filter except a transmittance peak in the stopband.Based on the analysis of the cross-sectional scanning electron microscopic image of the sample,it is found that the transmission peak is most likely to be caused by the instability of the deposition rate.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60506002 and 60776015, the Special Funds for Major State Basic Research Project of China No 2006CB604907, and National High-Tech R＆D Programme of China under Grant Nos 2007AA03Z402 and 2007AA03Z451.
文摘We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were deposited on nitrided sapphire, low-temperature InN （LT-InN） and high-temperature GaN （HT-GaN）, respectively. The InN layer grown directly on nitrided sapphire owns the narrowest x-ray diffraction rocking curve （XRC） width of 300 aresee among the three samples, and demonstrates a two-dimensional （2D） step-flow-like lateral growth mode, which is much different from the three-dimensional （3D） pillar-like growth mode of LT-InN and HT-GaN buffered samples. It seems that mismatch tensile strain is helpful for the lateral epitaxy of InN film, whereas compressive strain promotes the vertical growth of InN films.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)the Natural Science Foundation of Shanghai Committee of Science and Technology, China (Grant No. 10ZR1433500)
文摘In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phe- nomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and -lst transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in -lst transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented.
基金Supported by the National Natural Science Foundation of China under Grant No 60678004.
文摘Laser damage performance of multilayer films with combined irradiation of 1ω and 2ω is studied to probe the damage mechanisms during wavelength division. The laser induced damage thresholds （LIDTs） of the samples are obtained and tested with only 2ω with various energy densities of 1ω. Different 1ω; polarization directions combined with the 2ω case are also investigated. The result suggests that lw can raise the damage probability of multilayer mirrors when two light wavelengths are present simultaneously; the increasing number of sensitive defects for 2ω can be related to the decline of the LIDTs of the multilayer mirrors.
基金the National Natural Science Foundation of China(No.51871030)the Higher Education Science Foundation of Jiangsu Province of China (No.17KJA430006)。
文摘The interface structure and electronic properties of Fe(110)/Al(110) are investigated by the first-principles plane-wave pseudopotential method. The interface segregation position of Si and Mg is determined, and the effect of Mg and Si on the interface binding of Fe(110)/Al(110) is analyzed by combining the work of separation and charge density. The results show that the Fe(110)/Al(110) interface energy of FeHollow coordination is smaller and the interface structure is more stable. The Fe(110)/Al(110) interface separation surface in the form of Fe-Hollow coordination appears at the sub interface layer on the side of Al(110)near the interface. The interface structure of Mg and Si segregation is similar to that of undoped alloy elements.The calculations also suggest that Mg and Si segregate on the Al(110) side of the interface and occupy the Al lattice on the Al(110) side. The segregation of Mg and Si elements will reduce the interface binding, primarily because the Fe-Si bond and Fe-Mg bond are weaker than Fe-Al bond.
基金Supported by the National Natural Science Foundation of China under Grant No 10676019.
文摘By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is proved that laser conditioning is an efficient way to improve the damage resistance. The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps. We have also found that the damage resistance of the z-cut crystal is higher than the triplet cut, and the pinpoint number is definitely less in the z-cut crystal. The reason for these observations is discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10704079 and 10976030)
文摘A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technol- ogy. The optical properties of the composite films varying with the composition of the material are studied in detail, Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a re- flection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra axe in good agreement with each other, The causes of the slight differences between them are also analysed.
文摘The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.
基金supported by the National Natural Science Foundation of China under Grant No.10704078
文摘The evolution of stress in evaporated SiO2, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures （thin film deposition, stopping deposition, cooling, venting the vacuum chamber, and exposing coated optics to the atmosphere） is put forward. Further investigations into the subprocedures reveal their features. During the deposition stage, the stresses are usually compressive and reach a stable state when the deposited film is thicker than 100 nm. An increment of compressive stress value is observed with the decrease of residual gas pressure or deposition rate. A very low stress of-20 MPa is formed in SiO2 films deposited at 3×10^-2 Pa. After deposition, the stress increases slightly in the compressive direction and is subject to the stabilization in subsequent tens of minutes. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours. An initial discussion of these behaviors is given.
基金supported by the Shanghai Key Basic Research Program(No.09JC1414900)the Optics Science and Technology Foundation of Shanghai City (No.09DZ1142002).
文摘YAG：Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique （TGT）. The effects of annealing on the luminescence efficiency of YAG：Ce crystal are investigated, and the optimal annealing temperature and atmosphere are obtained. The mechanism of variation behavior of the luminescence efficiency of YAG：Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed.
基金supported by the Project of High Technology Research and Development of China under Grant No.2006AA03A101
文摘The growth of a Mn-doped LiAlO_2 single crystal by the Czochralski（CZ） method and the characterization of its spectroscopy and thermoluminescence（TL） are presented.The X-ray rocking curve and chemical etching analysis show that the as-grown crystal has good crystallinity.The full-width at half-maximum （FWHM） of the LiAlO_2（200）ωrocking curve is 23.2 arcsec and the etching pits density of the（100） plane is（1.6-4.0）×10~4 cm^（-2）.The transmission spectrum indicates that the crystal is highly transparent in the 200-1500-nm wavelength range.The emission spectrum of the crystal consists of a peak around 579 nm when excited with 428-nm light.The TL spectra show that the LiAlO_2：Mn crystal has glow peaks at 150 and 172℃.The change of TL characteristics of the crystal before and after thermal annealing in the air is discussed,and the effect of annealing and irradiation on the evolution of defect types is analyzed.
基金supported by the National"863"Program of China(No.2007AA03Z441)the National Natural Science Foundation of China(Nos.60607014 and 50572110)
文摘The emission properties of 2-um region fluorescence of Tm^3＋-Ho^3＋ co-doped tellurite glasses are investigated. Introducing F- ions to the composition of tellurite glasses plays a positive effect on the 2-#m emission. A maximum intensity of 2-um emission is achieved when 1.5-mol% Tm2O3 and 1-mol% Ho203 concentration are doped in the glasses. The emission cross section and gain coefficient of the ^5I8-^5I7 transition of Ho^3＋ are calculated. The emission cross section has a maximum of 1.29×10-20 cm^2 at 2048 nm wavelength. The results indicate that Tm＆3＋-Ho^3＋ co-doped tellurite glasses are suitable for 2-um application.
基金supported by the National Natural Science Foundation of China under Grant Nos.60878045 and 10976030
文摘In contrast to uncoated substrate, a nonlinear relationship of phase shift with the thicknesses of the thin film makes the calculation of wavefront aberration complicated. A program is compiled to calculate the wavefront aberration of multilayer thin film produced by thickness nonuniformity. The physical thickness and the optical phase change on reflection are considered. As an example, the wavefront aberration of the all-dielectric mirror is presented in ArF excimer lithography system with a typical thickness distribution. In addition, the wavefront errors of the thin film at wavelengths of 193 and 633 nm are compared in the one-piece and two-piece arrangements. Results show that the phase shift upon reflection of the thin film produced by thickness nonuniformity is very sensitive to the incident angle, wavelength, and polarization.
