孔径梯度变化的聚苯乙烯多孔薄膜的制备

 为了对聚合物多孔材料的微观孔结构进行控制,利用垂直沉积技术,制备了蛋白石结构和多层异质结构的SiO₂胶体晶体,并通过模板导向前驱物填充手段,获得了反蛋白石结构和孔径梯度变化的聚苯乙烯多孔薄膜。扫描电镜分析表明,聚苯乙烯多孔结构精确复制了原始模板的反结构。光学透射谱显示,填充聚苯乙烯后复合蛋白石光子禁带位置相对原始模板发生红移,除去模板后,光子禁带位置发生蓝移。根据布拉格衍射方程,计算出胶体晶体模板空隙的填充分数。     

CeO_2:Eu~(3+)反蛋白石的制备与性质研究

以自组装法制备的面心立方结构的聚甲基丙烯酸甲酯(PMMA)蛋白石为模板,采用溶胶凝胶法制备二氧化铈(CeO2)掺杂铕离子(Eu3+)的反蛋白石结构光子晶体.利用XRD,SEM,UV-Vis等测量手段研究了光子禁带特性,样品在低温下的发光特性也被研究.结果表明CeO2:Eu3+反蛋白石的光子禁带是413nm,PMMA蛋白石的光子禁带是612nm,与理论计算结果十分吻合.且随着温度的降低,Eu3+离子所处晶体场的对称性下降.     

低压化学气相沉积技术制备锗反蛋白石三维光子晶体

采用溶剂蒸发对流自组装法将单分散SiO2微球组装形成三维有序胶体晶体模板,用低压化学气相沉积法填充高折射率材料锗,酸洗去除SiO2模板,获得了锗反蛋白石三维光子晶体.通过扫描电镜、X射线衍射仪和紫外-可见-近红外光谱仪对锗反蛋白石的形貌、成分、结构和光学性能进行了表征.结果表明:锗在SiO2微球空隙内具有较高的结晶质量,填充致密均匀.通过改变沉积工艺,可控制锗的填充率;制备的锗反蛋白三维光子晶体具有明显的光学反射峰,表现出光学带隙效应.测试的光学性能与理论计算基本吻合.     

低压化学气相沉积技术制备锗反蛋白石三维光子晶体

采用溶剂蒸发对流自组装法将单分散SiO2微球组装形成三维有序胶体晶体模板,用低压化学气相沉积法填充高折射率材料锗,酸洗去除SiO2模板,获得了锗反蛋白石三维光子晶体.通过扫描电镜、X射线衍射仪和紫外-可见-近红外光谱仪对锗反蛋白石的形貌、成分、结构和光学性能进行了表征.结果表明：锗在SiO2微球空隙内具有较高的结晶质量,填充致密均匀.通过改变沉积工艺,可控制锗的填充率;制备的锗反蛋白三维光子晶体具有明显的光学反射峰,表现出光学带隙效应.测试的光学性能与理论计算基本吻合.     

低温等离子体增强化学气相沉积法制备Ge反opal三维光子晶体及其光学性能

通过溶剂蒸发对流自组装法制备SiO2三维有序胶体晶体模板,采用等离子体增强化学气相沉积法在200℃低温条件下填充高折射率材料Ge,获得了Ge反opal三维光子晶体.实现了低于GeH4热分解温度的低温填充.通过扫描电镜、X射线衍射仪和傅里叶变换显微红外光谱仪对Ge反opal的形貌、成分和光学性能进行了表征.结果表明:沉积得到无定型态Ge,退火后形成多晶Ge,Ge在SiO2微球空隙内填充致密均匀.Ge反opal的反射光谱有明显的光学反射峰,表现出光子带隙效应,其带隙中心波长为1650nm和2640nm,测试的光学性能与理论计算基本符合.采用SU-8光刻胶薄膜也进行了Ge沉积,证实了SU-8模板可以耐受这一沉积温度.低温沉积降低了Ge的填充温度,可以直接采用不耐高温的高分子材料作为初始模板,单次复型制备得到多种构型的完全带隙三维光子晶体.     

采用溶胶凝胶协同自组装与光刻相结合的方法在反蛋白石结构薄膜中引入二维缺陷

采用溶胶凝胶协同自组装与光刻相结合的方法,在光子晶体反蛋白石结构中引入缺陷,通过溶胶凝胶协同自组装方法在硅片上垂直沉积胶体晶体复合薄膜,把BP212正性光刻胶均匀旋涂在复合薄膜上,通过曝光、显影等光刻工艺,把掩膜版图案复制在复合薄膜上,用此样品再次垂直沉积一层复合薄膜,使图案被复合薄膜覆盖.最后去除胶体微球与光刻胶图案,从而在反蛋白石结构中引入缺陷,用扫描电子显微镜对样品进行表征.分析了光刻胶图案对胶体微球排列的影响.     

中红外完全带隙Si反蛋白石光子晶体的制备与光学性能研究

通过溶剂蒸发对流自组装法制备SiO2胶体晶体,采用低压化学气相沉积法填充Si,制备得到Si反蛋白石(opal)三维光子晶体.采用扫描电子显微镜对Si反opal的显微形貌进行表征,采用平面波展开法理论模拟Si反opal的光子带隙,采用傅里叶变换红外光谱仪测试其光学性能.研究结果表明:Si在SiO2微球空隙内填充致密均匀,显微红外光谱测试的光子带隙反射峰位置及带宽与理论计算基本符合.变角度反射光谱测试表明,Si反opal沿不同角度入射时在中心波长3319nm处均存在明显的反射峰,证明其具有完全光子带隙,带隙位于中红外大气窗口区域.     

圆柱形蛋白石和反蛋白石结构光子晶体的制备及其光学性质

研究了在圆柱曲面基底上自组装空心和实心的圆柱形蛋白石和反蛋白石结构光子晶体的方法. 用垂直沉积法在不同曲率半径的毛细管内自组装了空心圆柱形聚苯乙烯(PS)蛋白石结构光子晶体薄膜和二氧化硅 (SiO₂) 反蛋白石结构薄膜; 用类重力沉积法制得实心圆柱形蛋白石和反蛋白石结构光子晶体, 并讨论了这一生长方式中的状态变化过程及影响因素. 用扫描电子显微镜对样品内部结构进行了表征, 用光谱仪测试了光子晶体薄膜的反射光谱, 结果表明: 基底曲率半径和微球粒径的大小是影响空心蛋白石和反蛋白石薄膜质量的主要因素; 微球大小是影响实心结构有序性的主要因素. 关键词： 反蛋白石 空心圆柱 溶胶凝胶协同自组装     

蛋白石型光子晶体红外隐身材料的制备

基于光子晶体的红外隐身材料,主要采取一维层层堆叠结构和三维木堆结构等来实现对红外波段电磁波辐射性能的调控.本文报道了一种操作简易、成本低廉的光子晶体红外隐身材料制备方法.通过优化的垂直沉积法,微米级SiO_2胶体微球自组装成高质量的蛋白石型光子晶体结构.对SiO_2胶体微球进行优选,成功制备了禁带位于2.8—3.5μm,8.0—10.0μm的SiO_2胶体晶体蛋白石型光子晶体材料.该材料可改变目标相应波段的红外辐射特征,具有目标红外波段的隐身效果.     

采用溶胶凝胶协同自组装方法制备SiO2反蛋白石结构薄膜及其光学性质研究

研究了溶胶凝胶协同自组装制备大面积高质量SiO₂反蛋白石结构薄膜的方法. 向单分散的聚苯乙烯(PS)胶体溶液中添加SiO₂前驱物溶液,用垂直自组装法一步得到微球空隙中均匀填充有凝胶的 复合PS胶体晶体薄膜,在空气中烧结去除PS后得到SiO₂反蛋白石结构薄膜.通过对添加前驱物溶液比例、 自组装温度以及烧结温度等参数的研究,用不同粒径的PS微球制备了不同孔径的高质量SiO₂反蛋白石结构薄膜. 用扫描电子显微镜和X射线能量色散谱仪对制备得到的薄膜样品进行显微形貌和成分表征,并测试了其透射光谱. 结果表明:溶胶凝胶协同自组装法制备的SiO₂反蛋白石结构薄膜大面积高度有序,孔径可以控制且选择范围宽; 薄膜的透射光谱带隙明显,带隙中心波长与理论计算结果相符.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.