Z扫描法测单壁碳纳米管薄膜非线性特性的研究

为研究单壁碳纳米管(SWCNT)薄膜的三阶非线性光学性质,采用旋转涂覆法在石英玻片上制备出包含SWCNT和聚甲基丙烯酸甲酯(PMMA)的聚合物薄膜。测得薄膜的线性透射谱,并观察了薄膜的表面形貌。为提高测量SWCNT薄膜三阶非线性系数的准确度,研究了Z扫描法测量材料的非线性系数时相关参量变化对测量准确度的影响,并搭建Z扫描系统,研究了自制薄膜的三阶非线性光学性质。通过对实验数据的模拟和计算,得到自制碳纳米管薄膜的非线性吸收系数(β)、三阶非线性折射系数(γ)分别为-7.8×10-7 cm/W、-6.4×10-11 cm2/W,三阶非线性极化率为2.06×10-9 esu。证明SWCNT/PMMA薄膜具有较强的非线性光学特性。     

High-frequency reflection from the aperture of a long E-planesectoral horn

The result of Yee et al. (1968) for the parallel-plane TE₁₀ -mode reflection coefficient, used in Jull's (1972) formulation for the reflection coefficient of a long E-plane sectoral horn, is replaced by the Boersma's (1974) corresponding result. At longer wavelengths, the expression that emerges displays a much better match with experiments than Jull's original expressions     

Surface-acoustic-wave bandpass filters on ZnO/Pyrex substrate with zero temperature coefficient

Thick layers of ZnO (5?10 ?m) deposited on Pyrex glass have been investigated in order to realise low-cost and temperature-stable surface-acoustic-wave bandpass filters. We describe the sputtering method used to grow the ZnO layer and we give the measured results of the acoustical and thermal properties for different film thicknesses. A high coupling coefficient (10%) and very good temperature stability (zero first-order and 1 × 10?8/(°C)2 second-order temperature coefficient) are reported. In addition we show results obtained on an 8% 1 dB relative bandwidth filter operating around 110 MHz which demonstrate that this new piezoelectric substrate leads to filters with better properties than those achieved on ST-cut quartz substrate.     

溶胶-凝胶法制备Zn2+掺杂MgO薄膜及光电性能表征

采用溶胶-凝胶(sol-gel)法,利用旋转涂覆技术在玻璃衬底及单晶Si(111)衬底上制备掺Zn2+的MgO薄膜。使用紫外可见光分光光度计测定掺杂薄膜的透过率,并采用XRD和EDS等测试手段研究薄膜的晶向结构和成分。结果表明,胶棉液的含量对成膜质量有重要的影响;随着Zn2+掺杂量的提高,薄膜透过率先增大后减小,在掺杂量为10%时,薄膜有最佳透过率;随着退火温度的升高,薄膜晶粒生长没有出现明显的择优取向。最后,对模拟放电单元进行放电测试,结果表明,在掺杂量为10%时,薄膜有最低着火电压和最高的记忆系数。     

基于光热位移原理的KDP晶体光吸收系数干涉测量方法的数学模型及结构参数优化

KDP晶体的光吸收系数是评价其光学质量的重要参数。尤其在惯性约束核聚变装置（ICF）中,其大小直接决定出射脉冲的能量及频率转换效率,因此必须对它进行高精度测量。KDP晶体光吸收系数的数量级一般在10-3/cm~10-5/cm,传统的光吸收系数检测方法已经无法满足该测量分辨率要求。文中针对KDP晶体的特点提出了一种基于光热位移原理的干涉测量方法来解决其吸收系数精密测量的问题。首先利用积分变换思想建立了KDP 晶体光吸收系数干涉测量数学模型,然后基于该模型对测量系统的结构参数进行了仿真优化,得到了系统的设计参数。     

一种新型有机金属化合物的三阶光学非线性研究

为了研究一种新型有机金属化合物(十六烷基三甲基铵)双(1,3-二硫杂环戊烯-2-硫酮-4,5-二硫基)-镍(简称CTNi)的三阶非线性光学性质,配制了浓度为1.0×10-4mol/L的丙酮溶液作为待测样品,采用Z扫描测试技术,在波长为1064 nm,脉宽为40 ps的条件下研究了该样品的三阶非线性光学性质.研究发现,该材料具有很强的饱和吸收特性,其激发态有效吸收截面为eσff=1.47×10-18cm2,相应的非线性吸收系数β=-4.36×10-12m/W.另外,Z扫描曲线显示该材料还具有较强的自散焦效应,其三阶非线性折射系数n2=-1.55×10-18m2/W.     

后固化对树脂传递模塑成型复合材料性能影响监测

研制了双光纤Bragg光栅(FBG)温度/应变传感器,监测二次后固化对树脂传递模塑(RTM)成型复合材料的应变自由温度、玻璃化转变温度、残余应变及热膨胀系数的影响规律,并分析模具材料对热膨胀系数的影响。实验结果表明,二次后固化后,复合材料应变自由温度和玻璃化转变温度分别从189.0℃、189.4℃增加到200.2℃、204.0℃;外层残余应变从-597.7με下降至-671.5με;外层复合材料热膨胀系数从5.248×10-6/℃下降为4.275×10-6/℃,说明后固化可显著提高复合材料性能。     

基于Berreman矩阵研究一维掺有各向异性材料缺陷的光子晶体偏振特性

为了研究具有各向异性材料缺陷层的光子晶体禁带特性,构造了具有各向异性材料缺陷层（AB）10F（BA）10 型一维光子晶体,利用Berreman 传输矩阵进行了数值计算。研究发现,随着缺陷层F 厚度d的增加,在700~1 000 nm 禁带中出现的两个缺陷模发生红移,缺陷模透射系数呈阶段性变化。改变缺陷层内单轴晶体方位角 ,X偏振光产生的缺陷模往长波方向移动,透射系数在一定波长范围内规律变化,而Y偏振光产生的缺陷模始终不变。另方位角在0~90范围内变化,则该禁带内产生新的缺陷模。缺陷模的这些特征对全方位过滤器的设计有一定价值。     

Self-focusing of 10.6-µm radiation in liquid CS2

Self-focusing of 9-kW CO2laser pulses was observed in liquid CS2. The calculated coefficient of nonlinear index of refraction (n2) from experimental data is approximately 10^-17MKS, which is nearly three orders of magnitude larger than the nonlinear index coefficient observed for visible radiation.     

弛豫铁电单晶PMNT压力稳定性的研究

采用密闭油腔产生静压力,样品置于油腔内,测试了(001)切型弛豫铁电单晶0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(简写为PMNT67/33)的介电常数和静水压压电常数的压力稳定性。结果显示:随压力增大,εr缓慢增加,压力在10MPa内其相对变化小于1.8×10-2,tgδ无显著变化;压电常数dh和gh先显著下降,至2MPa后趋于稳定。结果表明,弛豫铁电单晶PMNT施加一定的预应力后,性能随静压力的变化趋于稳定。     

BSTO移相器材料结构与温度特性的研究

为了改进BSTO/MgO系铁电移相材料的电学性能,研究了在同等掺杂条件下,调节Ba1–xSrxTiO3中各成分的配比,即改变x的取值对材料结构及温度特性的影响。实验表明:当x=0.45时,BSTO/MgO系统在10kHz下,εr=84.45;tanδ=3.4×10–3;可调率为11.01%(5kV/mm)。3.5GHz下,εr=87.01,tanδ=4×10–3,并具有相对较好的温度稳定性,在–20~+40℃下αεr=–0.482×10–2/℃,可调率温度系数为–0.836×10–2/℃。     

基于MOSFET ZTC工作点的高阶曲率补偿电压基准

工作在饱和区的MOSFET存在零温度系数(ZTC)特定工作点,基于这一特性设计实现了一款具有低温度系数的电压基准芯片。所设计的电路利用ZTC工作点的温度系数接近于0这一特点,辅以高阶曲率补偿电路,实现极低温度系数的输出电压。此外,针对ZTC工作点对工艺偏差的敏感性,根据蒙特卡洛仿真结果,专门设计了熔丝修调电路,以保证电路的输出结果具有较高工艺稳定性。该电路在CSMC 0.18μm CMOS工艺平台进行了流片验证,芯片面积为0.0025 mm²。结果表明该芯片在室温时能够稳定输出475.5 mV电压,在-40~125℃内,温度系数达到1.8×10^-6/℃,在10 kHz时电源抑制比达到-68.7 dB。     

Spatial Distribution of the Seebeck Coefficient in Zn<Subscript>13</Subscript>Sb<Subscript>10</Subscript> Determined by a Seebeck Microprobe Measurement System

A Seebeck microprobe (SMP) measurement system has been developed and employed to determine the spatial distribution of the Seebeck coefficient of a polycrystalline Zn₁₃Sb₁₀ specimen prepared by a gradient freeze (GF) method. The spatial distribution of the Seebeck coefficient strongly reflects that of the grains observed using an optical polarizing microscope, the magnitude of which ranges from 100 μV/K to 130 μV/K. This fact strongly indicates that the observed spatial distribution of the Seebeck coefficient arises from the anisotropic Seebeck effect of grains with different crystal orientations in the polycrystalline Zn₁₃Sb₁₀.     

Novel type of fibre-optic ring resonator

A fibre-optic ring resonator with highly wavelength-selective input reflection coefficient was realised by introducing a small local reflection in the ring. The influence of the local reflectivity on the input reflection coefficient is demonstrated. Maximum values for the input reflectivity and finesse are 55% and 10, respectively, using a fibre directional coupler (FDC) with a coupling ratio of 30%/70%.     

一种高精度低压差线性稳压芯片的实现

文中介绍了一种提高低压差线性稳压芯片输出电压精度的技术,该芯片使用了能隙基准的温度补偿技术,克服了能隙参考电压在通常使用的温度范围(10℃～100℃)内的温度漂移,从而使稳压芯片输出电压的温度系数从普通的约100×10~(-6)℃降至20.2×10~(-6)℃。     

Measurements of the InGaAs hole impact ionization coefficient inInAlAs/InGaAs pnp HBTs

The hole multiplication factor in pnp InAlAs/InGaAs single heterojunction bipolar transistors (HBTs) has been measured as a function of the base-collector bias. The hole impact ionization coefficient β_p has been estimated taking into account the Early effect, I_CBO, and thermal effects. Numerical corrections for dead space were made. The importance of considering second order effects is highlighted, showing that rough approximations can lead to an overestimation of the coefficient β_p. At low electric fields, the extracted coefficient agrees with the most recent photomultiplication measurements available in the literature. At high electric fields, hole impact ionization coefficient is estimated up to values previously not reported in the literature (β_p≈10⁴ cm^-1)     

CaO对MgO-Al2O3-SiO2微晶玻璃烧结和性能的影响

研究了氧化钙对MgO-Al2O3-SiO2系微晶玻璃烧结特性和性能的影响。结果表明:氧化钙替代氧化镁能够促进微晶玻璃粉体的烧结致密化,影响玻璃的晶化特性、介电性能和热膨胀特性。随着氧化钙量的增加,样品的介电常数和热膨胀系数增加,但其介质损耗呈现先减小后稍微增加的趋势。含3%CaO(质量分数)的样品可在900℃烧结致密化,并具有低的εr(5.4)、低的tgδ(≤0.13×10-2)和低的α(3.55×10-6℃-1),是一种有应用前景的低温共烧陶瓷基板材料。     

Gain saturation coefficients of strained-layer multiple quantum-well distributed feedback lasers

The gain saturation coefficients were measured for strained and unstrained multiple quantum-well distributed feedback (MQW-DFB) lasers. The gain saturation coefficient depends on the deviation of the laser's transverse-magnetic (TM) mode gain peak wavelength from its transverse-electric (TE) mode gain peak wavelength delta lambda , which is related to the strain on the active-layer wells. The gain saturation coefficient epsilon increased with increasing compressed strain on the active-layer wells. The coefficient epsilon of the unstrained MQW DFB laser with a wavelength deviation delta lambda of -350 AA was 2.45*10/sup -17/ cm/sup 3/, and epsilon increased up to 12.6*10/sup -17/ cm/sup 3/ in the SL-MQW DFB laser with a wavelength difference delta lambda of -890 AA.<>     

Complex Permittivity of GaAs and CdTe at Microwave Frequencies

The microwave dielectric constant and loss tangent of Cr-doped semi-insulatiug GaAs have been measured in the frequency range 2.5-36.0 GHz and the temperature range 300-400 K. The room temperature dielectric constant is 12.95 and the temperature coefficient alpha ( /spl equiv/ epsilon(0)/sup -1/ d epsilon/dT) is 1.6 x 10/sup -4/ /K. The dielectric constant and loss tangent of CdTe have been measured as functions of temperature at 15.95 GHz. The room temperature dielectric constant is 10.39 /spl plusmn/ 0.04 and the temperature coefficient alpha is 2.5 x 10/sup -4/ /K.     

硫掺杂对ZnO热电性能的影响

采用固相反应法制备了ZnO1-xSx块体材料(0≤x≤0.05);通过对样品X射线衍射谱(XRD)、电导率和Seebeck系数的测量,研究了S掺杂对ZnO晶体结构及热电性能的影响。结果表明:所有试样均为六方纤锌矿结构。在573 K时,ZnO1-xSx(0相似文献