原子光刻中驻波场与基片距离的判定方法研究

原子光刻实验中, 激光驻波场能起到原子透镜的效果, 实现原子汇聚. 激光驻波场与沉积基片间的距离对形成纳米条纹结构的质量具有重要影响. 利用高斯光束传播规律, 提出了一种能够定量判断激光驻波场与沉积基片相对位置的实验方法. 该方法通过调节装载有凸透镜和反射镜的精密位移台改变驻波场距基片的距离, 利用光电探测器接收反射光强的变化, 将位移改变量转变为接收器的电压信号. 利用驻波场激光束光斑直径值, 实现准确定位驻波场与基片的距离. 对上述实验过程进行数值模拟, 数值计算的结果和实验结果高度符合. 该方法实现了准确定位驻波场距基片的距离, 为后续深入研究驻波场和基片间距离对沉积纳米条纹结构质量的影响提供实验基础.     

电子在线极化相对论强度驻波场中的散射研究

研究了线极化相对论激光驻波场中的电子运动,分析了偏振面内入射的电子在激光驻波场中的散射与电子初始位置、能量以及激光强度的关系.结果表明,电子在驻波场中的散射情况与电子对激光的相对能量γ₀/a₀密切相关.对于同样的激光强度,电子初始能量存在一个能够发生前向或背向散射的临界值.光强越大,电子发生前向散射的初始能量临界值越大.用电子相对能量来衡量,这个临界值大约在1.0一1.25范围内.当相对能量超过该值,电子运动会从背向变为前向散射.电子在驻波场中的振荡中心和有质动力逆转效应的存在也是有条件的,二者只有电子相对能量γ₀/a₀在一定取值范围内才可能存在.相对能量越小,电子能发生前向散射的入射驻波面越小,而低能电子更倾向于从波节透过.在偏振面内入射的电子在高强度驻波场中会发生非弹性散射,电子与场会发生高能量交换.     

抽运光强度对光学抽运重水气体产生THz激光的影响分析

利用半经典理论，对脉冲光学抽运重水气体产生THz激光信号过程进行分析，对其中抽运光强度与输出THz信号光之间的关系进行了数值计算和求解，结果表明，THz信号出射光强度跟抽运源入射光强度之间不满足简单的线性关系，而是呈现高阶的非线性关系.在工作介质腔长、气压和工作温度一定的条件下，存在最佳抽运光强度，在一定的抽运光强范围内，THz信号出射光强度与抽运源入射光强度的关系呈现近似线性的增长关系，抽运光能量和信号光能量之间的转换效率相对较高，当抽运光强超过一定值时，由于瓶颈效应的发生会导致THz输出信号的逐步减弱，并产生一定的频率调谐范围.     

驻波法测量声速实验的讨论

根据声波在2个换能器之间多次反射和声波在空气中的衰减,研究了驻波法测量声速实验中接收器输出信号随接收器到发送器间距离的变化.理论推导结果表明:声波在一般情况下不是严格的驻波,但是当反射比接近-1时则是双曲函数形式的驻波,这与实验测量结果一致.只有接收器到发送器的距离比较远,反射比接近-1时,才能得到几乎理想的驻波.     

折射率色散效应对晶体硅太阳电池反射率的影响

为了分析色散效应对晶体硅太阳电池反射率的影响,在考虑材料折射率色散效应的情况下,运用光学干涉矩阵计算了具有SiO2单层减反射膜和MgF2/ZnS双层减反射膜晶体硅太阳电池的反射率与波长的函数关系,并与实验结果和未考虑色散效应的计算结果进行了对比分析.结果表明：考虑折射率色散效应的计算结果与实验测量数据完全相符,而未考虑折射率色散效应的计算结果与实验测量数据相差较大,最大差值分别为21.5％和16.9％.     

一维矩形刻槽相位栅的减反特性与结构优化

 为了得到一种结构简单、便于制作的可应用于可见光波段的减反射膜,利用等效介质理论研究了表面具有矩形刻槽周期分布形式的介质膜的减反射特性,比较了4种不同基底材料的减反特性,选用聚甲基丙烯酸甲酯（PMMA）作为基底分析了一维单层矩形光栅结构的减反射膜的占空比、蚀刻深度、入射波长和入射角度对减反射特性的影响;给出了可见光波段的减反射膜的结构设计参数。研究结果表明：当入射角小于30°时,可见光中的短波段（0.4 μm～0.55 μm）反射率低于2%;当入射角小于10°时,该减反射膜可以使0.4 μm～0.8 μm可见光的反射率低于2%。     

扫描干涉场曝光中光栅掩模槽形轮廓的预测

根据扫描干涉场曝光的特点,针对光刻胶层内曝光量的驻波效应,建立了动态曝光模型。基于快速推进法建立了显影模型,得到了光栅掩模槽形的演变规律。为减弱驻波效应的影响,提出了一种抗反射层最优厚度的设计方法。仿真结果表明,建立的曝光和显影模型能有效预测光栅掩模的槽形轮廓,同时可优化抗反射膜的厚度。     

衣物在潮湿时变暗的光学分析

通过理论推导和实验探究,从反射、折射、吸收方面阐述了衣物在潮湿时会变暗这一现象的产生机理.当衣物被浸湿后,由于光在浸湿液面内的不断反射和折射使得最后反射到人眼的光强大大减弱,同时由于光在液体内的吸收又使反射的光强减弱,从而看到衣物在潮湿时变暗.     

超宽带减反射膜的设计和制备

设计了400～900 nm波段上的超宽带减反射膜,在410～850 nm范围内的平均残余反射率设计值约为0.2%,在设计的全波段上约为0.24%.讨论了初始膜系结构的选择原则,分析了带宽、膜层折射率差、最外层折射率和膜层总厚度等因素对宽带减反射特性的影响.对特定的带宽.增加两种薄膜材料的折射率差和选择尽可能低的最外层折射率对获得优良的减反射特性是非常重要的.实验制备了K9玻璃上TiO2/MgF2两种材料组成的8层结构的超宽带减反射膜,实测结果表明,在带宽520 nm范围内的平均残余反射率约为0.44%,说明用二种材料设计超宽带减反射膜是成功的,对垂直入射的减反射膜.多种材料的膜系并不比两种材料更具优越性.     

多壁碳纳米管光限幅特性的研究

用化学气相沉积法制备了多壁碳纳米管,并将其溶解在甲苯溶液中.用波长为1064nm的皮秒脉冲激光测量该样品的透过率,发现了非常明显的光限幅特性.当入射光强较小时,透射光强度随入射光强度的增大而增大,输出与输入为线性关系;随着入射光强的增大,透射光强增长的速度明显变慢,并逐渐趋于饱和.当入射光强度较小时,样品的透过率接近100%;而当入射光强为8GW/cm²时,非线性透过率达到30%.根据三光子吸收理论计算,理论拟合与实验结果非常符合,说明多壁碳纳米管的三光子吸收产生了光限幅效应.实验测 关键词： 多壁碳纳米管 光限幅 三光子吸收     

利用光学薄膜模型研究垂直腔面发射激光器的光学特性

可以把垂直腔面发射激光器看作是多层光学薄膜,应用光学薄膜原理对其光学薄膜的特性进行了研究。计算分析了布拉格反射镜和谐振腔模的反射谱受器件结构变化的影响。通过利用菲涅耳系数矩阵法计算,得到了光在垂直腔面发射激光器器件结构中形成的驻波场分布。结果表明,利用菲涅耳系数矩阵法设计垂直腔面发射激光器的光学薄膜是一种快捷准确的方法。     

X-ray circular dichroism under reflection from antiferromagnetically coupled multilayers

The fluorescence yield under the Bragg reflection of right and left circular polarized radiation with a wavelength in the vicinity of the FeL _{2, 3} absorption edges from the periodic multilayer [Fe(1.5 nm)/V(1.5 nm)]₁₀ that is characterized by the antiferromagnetic interlayer exchange coupling has been theoretically analyzed in L-MOKE geometry. It has been shown that the largest polarization asymmetry of reflectivity takes place at the ??magnetic?? Bragg reflection, which appears due to the doubling of the magnetic period. The expected occurrence of the dichronic signal in the fluorescence yield by its selective excitation in the layers with the same magnetization direction was confirmed, but the effect is suppressed by the specific behaviour of the standing waves in the strongly absorbing multilayers where the standing wave antinodes are situated in layers with low absorption.     

Mo/Si多层膜表面保护层设计

为提高Mo/Si多层膜的稳定性与使用寿命,通过分析多层膜驻波电场的分布,对表面保护层及多层膜最上层材料的厚度进行优化设计,使优化后的反射率最高.计算表明,一定厚度的表面保护层总对应一个最优的最上层材料厚度.在13.36 nm波长,膜对数为50的Mo/Si多层膜10度入射的理论反射率为74.47%;当添加厚度为2.3 nm的Ru作为表面保护层,对应多层膜最上层Si的优化厚度为3.93 nm,其理论反射率为75.20％.设计结果表明,通过优化设计表面保护层,可以提高多层膜稳定性,改善多层膜性能.     

Build-up processes of an optical cavity enclosing an absorbent thin film: computational study by the CIP method

Propagation of monochromatic light is analyzed by numerical calculations for an optical cavity enclosing a thin absorbent film. The computational study is performed by the CIP (constrained interpolation profile) method, which is shown to be able to solve temporal evolution of Maxwell’s equations even in a strongly absorbing medium. Simulations on build-up processes reveal that such a cavity exhibits transmittance even higher than the intrinsic transmissivity of the absorbent, i.e., the absorbent is virtually transparent, when the following requirements are satisfied: the film is much thinner than the wavelength, it is located at a node of a standing wave, and the cavity consists of a pair of mirrors with optimal reflectivity depending on the film thickness. Optimal conditions are discussed as well for maximizing absorption in the film.     

超高压下冲击波速度直接测量技术

针对超高压下透明材料的高压离化机理,分析了透明材料中冲击波直接诊断技术的基本方法. 利用Drude-自由电子气模型,分析了不同冲击压力下冲击波阵面反射率的变化. 从理论上比较了不同探针光波长反射率的区别,发现探针光波长为660 nm时比探针光波长为532 nm时获得的冲击波阵面反射率要高. 对探测器"致盲"问题也进行了研究. 通过分析反射信号的时间顺序和强度大小,发现"致盲"效应是由X光对透明窗口离化引起的. 同时,发现方波驱动脉冲平台的前沿到达时刻和X光离化效应出现的时刻相同,冲击波信号到达时刻晚于X光离化时刻. 通过实验结果,得到蓝宝石中冲击波速度为35 km/s时,其波阵面的反射率约为40%. 通过理论分析和实验数据比对的方法,验证了蓝宝石中的减速曲线. 给出了加蓝宝石窗口后的测速公式. 经过和实验对比,确认了测速公式的正确性. 关键词： 冲击波 光学诊断 成像 干涉仪     

Study of nano-scale diffusion in thin films and multilayers

It is shown that x-ray reflectivity and x-ray fluorescence under standing wave conditions can be used to study atomic diffusion with an accuracy of a fraction of a nanometer. Both the techniques can be made isotope selective by making use of nuclear resonance scattering from a Mössbauer active isotope. The techniques have been used to study self-diffusion of Fe in amorphous and nano-crystalline alloys of FeZr and FeN. The observed correlation of the activation energy E with pre-exponent factor D₀ confirms that in amorphous FeZr alloy diffusion takes place via collective motion of a group of atoms. Even in nanocrystalline alloys it is found that atomic diffusion occurs mainly through grain boundaries which are amorphous or highly disordered in nature.     

一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振     

Depth Resolved Structural Studies in Multilayers Using X-ray Standing Waves

X-ray based characterization techniques are powerful tools for the study of atomic scale structure of materials. However, high penetrating power of X-rays make them less suitable for depth selective studies, as required in the characterization of multilayer structures. In the present work, it is shown that depth selectivity of the techniques like, X-ray fluorescence, X-ray absorption spectroscopy and nuclear resonance fluorescence can be greatly enhanced by generating X-ray standing waves inside the multilayer structure. The concentration profiles of various elements can be obtained with a depth resolution of the order of 0.1 nm. Depth dependent information about the local structure around a given atom can be obtained from XAFS under standing wave conditions. It is demonstrated that detection of nuclear resonance fluorescence by tuning the energy of the incident X-rays to a Mössbauer transition can yield depth profile of a particular isotope, and can be used for self-diffusion studies. The techniques of X-ray reflectivity and conversion electron Mössbauer spectroscopy are used to provide useful complementary information.     

Layered Synthetic Microstructures (LSM): Reflecting media for X-ray optic elements and diffracting structures for the study of condensed matter

During the past two decades techniques for synthesis of superlattices, Layered Synthetic Microstructures (LSM) in the following, have been developed to a sufficiently high level for the product structures to be used as reflecting media in x-ray optics. Additionally, since this application requires high absolute reflectivity, LSMs may be used in both traditional and unique ways to study condensed matter. A short review of synthesis processes will be given as background, with emphasis on process parameters important in LSM deposition. A short review of the reflectivity/wavelength relationship over the spectral range 1 to 500 Å is then given. Experimental results for simple planar LSM structures are then discussed with emphasis on the effects of structural imperfections and engineered variations such as those necessary to construct LSM Fabry-Perot etalons. Results for experiments in which LSMs were used as reflecting/diffracting structures for evanescent and standing wave fluorescent scattering studies will be presented and the implications of these results discussed.     

The recoil effect in a strong electromagnetic field

The recoil effect in a strong resonance field of a standing electromagnetic wave has been studied. In order to find the response to the external field (the induced dipole momentum) it is necessary to take into account the variations in the motion of the atoms in this field: the response and the energy spectrum of the atoms are determined from the system of wave equations for the multi-level atoms. The problem of a weak signal absorption in the presence of a strong standing wave which is in resonance with the adjacent transition, is solved. In this case the contour of the absorption line is shown to diverge into two wide bands, their width being proportional to the strong field amplitude. The contribution of continuous and discrete states of the atoms in a standing wave field has been found.