Angular spectrum analysis of near-field diffraction of a small aperture

The near-field diffraction of a nanometer aperture is studied in this paper according to the angular spectrum theory. The mathematic expressions of the near-field diffraction are presented, and the influences of the polarization of the electromagnetic field and the evanescent wave on the diffraction in near field are analyzed by means of vector and scalar diffraction theory, respectively. The transverse and longitudinal diffraction intensity distributions of a small aperture are numerically calculated, and the results show the near-field diffraction of a small aperture is influenced strongly by the vector property of the electromagnetic field and the evanescent component.     

Super-transmission of light through subwavelength annular aperture arrays in metallic films: Spectral analysis and near-field optical images in the visible range

This paper presents experimental studies of the enhanced light transmission through metallic films pierced by subwavelength annular apertures. Two different methods (e-beam lithography and focused ion beam) have been used to build the nano-structures. We have experimentally recorded their far-field spectral response in the visible range and the optical near-field above the nano-structures when they are excited at 633 nm. The spectral response exhibits a transmission peak at 700 nm with maximum efficiency around 16%. The near-field exhibits a characteristic two-lobe structure just above the aperture. Finite difference time domain (FDTD) simulations reproduce quite well the experimental results.     

Theoretical study of optical recording with a solid immersion lens illuminated by focused double-ring-shaped radially-polarized beam

Based on the Richards–Wolf vector diffraction theory, the intensity distributions in the recording sample near a solid immersion lens are calculated for two different radially-polarized beams ( and modes). Numerical results show that a double-ring-shaped mode focusing has some excellent features in near-field optical storage, compared with a single-ring-shaped mode focusing. The recording density is markedly improved, the focal depth of the near-field recording system is substantially increased, and a subsurface recording is effectively obtained using the mode focusing.     

组合变形镜对板条固体MOPA激光波前畸变校正（英）

提出了一种利用组合变形镜校正板条MOPA固体激光器像差的方法,并通过实验验证其有效性。通过将一个11单元的一维变形镜和一个67单元的二维变形镜组合,有效降低了单个二维变形镜波前校正过程中驱动器间的电压差,从而提高了二维变形镜的使用安全性,并在一定程度上改善了校正后波前畸变的空间分布,降低了波前畸变残差。实验结果表明,一维变形镜与二维变形镜的组合能高效地校正板条MOPA固体激光器的波前畸变,波前残差均方根值小于0.08 m,远场光束质量因子可达1.67。     

共孔径偏振耦合分光的旋转四分之一波片相位补偿技术

 在地平式折轴望远镜中开展自适应光学激光导星实验,研究了共孔径发射接收信标激光束偏振耦合分光效率随望远镜方位角和天顶角变化的补偿技术。提出了一种由四分之一波片和法拉第旋光器构成的相位补偿器,通过旋转四分之一波片以实时补偿由于望远镜旋转导致的光路相位延迟量的变化。数值计算表明,望远镜处于任意方位角和天顶角位置时,通过1°步长旋转四分之一波片,可使补偿后的偏振分光效率理论上达到99.90％以上。实验从原理上定性地验证了该方法的有效性。只要测量出镜面的相位延迟,便可计算得到望远镜处于不同方位角和天顶角情况下有效补偿所需的四分之一波片旋转角度,据此可建立实用的旋转波片偏振补偿装置。     

共孔径偏振耦合分光的旋转四分之一波片相位补偿技术

在地平式折轴望远镜中开展自适应光学激光导星实验,研究了共孔径发射接收信标激光束偏振耦合分光效率随望远镜方位角和天顶角变化的补偿技术。提出了一种由四分之一波片和法拉第旋光器构成的相位补偿器,通过旋转四分之一波片以实时补偿由于望远镜旋转导致的光路相位延迟量的变化。数值计算表明,望远镜处于任意方位角和天顶角位置时,通过1°步长旋转四分之一波片,可使补偿后的偏振分光效率理论上达到99.90％以上。实验从原理上定性地验证了该方法的有效性。只要测量出镜面的相位延迟,便可计算得到望远镜处于不同方位角和天顶角情况下有效补偿所需的四分之一波片旋转角度,据此可建立实用的旋转波片偏振补偿装置。     

共孔径偏振耦合分光系统中反射镜造成的相位延迟差的测量

 激光信标共孔径发射接收偏振分光系统的动态相位补偿需要测量望远镜各反射镜对s光和p光的相位延迟差。利用Stokes矢量和Mueller矩阵建立了物理模型,并推导出用测得的回光功率计算相位延迟差的解析式。提出一种通过实验测量回光功率计算反射镜相位延迟差的方法,解决了在0～2p范围内唯一确定反射镜相位延迟差的问题。实际测量了两块反射镜的相位延迟差,并将测量结果用于动态相位补偿偏振分光实验,验证了该方法的正确性。分析了偏振分光棱镜、法拉第旋光器以及近似计算这3个主要的测量误差源,并估计总测量误差约为1°。     

利用扫描近场红外显微镜对化学样品组分进行成像研究

介绍了用北京自由电子激光为光源的扫描近场红外显微镜对化学样品组分进行的成像研究，通过所得到的近场微区图像，可以对样品在微区范围内的成分组成，混合的均匀程度等作出比较清晰的判断. 关键词： 自由电子激光 近场光学 扫描近场红外显微镜     

部分相干修正贝塞尔高斯光束通过球差透镜的聚焦特性

由部分相干光的传输理论出发,对部分相干修正贝塞尔高斯光束通过球差透镜聚焦后轴上光强分布进行了研究.数值计算表明:当光谱相干度较小时,正、负球差对应的最佳聚焦点位于无球差时对应的最佳聚焦点的两侧;当光谱相干度较大时,正、负球差对应的最佳聚焦点将位于无球差时对应的最佳聚焦点的左侧.研究进一步表明,最佳聚焦点随着透镜菲涅耳数的增大向几何焦点方向靠近,并趋于一个定值.当光束菲涅耳数为1时,无球差时对应的最佳聚焦点逐渐趋于0.908,该值与光谱相干度无关,当透镜具有球差时,该值与光谱相干度有关.     

Construction of an electron analyzer with a wide acceptance solid angle

We have developed a new electron energy analyzer with a large solid angle of 0.14π, which is comparable to that of cylindrical mirror analyzer. Typical energy resolution was ΔE/E₀ ∼ 0.016 for the aperture of 1 mm and central radius of 100 mm, and typical angular resolution was less than 0.5°.     

改进的正方形格点双芯光子晶体光纤的负色散特性分析

设计了一种改进的正方形格点双芯负色散光子晶体光纤,其包层是由在纯硅背景上以正方形格点排列的三种大小不同的空气孔构成,这些空气孔和中心的缺陷形成了这种负色散光子晶体光纤的双芯.用频域有限差分法对其分析表明,该光子晶体光纤具有宽带负色散的特性.当相邻空气孔间距取2.05 μm,空气孔直径分别取1.9 μm,1.3 μm,0.9 μm时,可在1.55 μm处实现宽带负色散,其半峰全宽超过了300 nm.这种光纤可用于波分复用光纤通信系统中的宽带色散补偿.     

Locally rigorous electromagnetic analysis of non-periodic gratings with large size and small features in the non-scalar validity domain by the field stitching method

Scalar theory is a simple and rapid method to analyse and conceive diffractive optical element and gratings, in some limited cases. When we want to deflect wave fronts with large angles (for telecommunication devices, for instance) or when the features of the grating are around the order of the wavelength, scalar optics fail to be accurate, then adapted rigorous electromagnetic tools must be used. To correct the increasing cost in memory saving and time consuming with the size of the grating, we present here an original `field stitching' method adapted for aperiodic gratings (FSA). This method, initially developed for periodic gratings is extended here to analyse locally and rigorously aperiodic gratings with large sizes and small features without having some of the above-mentioned inconvenients.     

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利用HL-2A装置实验数据,初步建立了面向ITERL DB2.0版本的能量约束数据库,采用了统计分析系统(SAS)对HL-2A约束数据进行了分析和评估,开展了能量约束时间对密度的定标律研究,并得到了初步结果。最后通过与ITER定标律和原ASDEX数据的比较,对HL-2A装置上L-模约束品质和欧姆加热条件下斯必泽电阻率对温度的依赖关系进行了讨论。     

The analysis of superconducting thin films modified by AFM lithography with a spectroscopic imaging technique

A practical application of nanolithography using atomic force microscopy (AFM) was accomplished in fabricating superconducting flux flow transistors (SFFTs). It was found that it is essential to oxidize a superconducting thin film, grown on LaAlO₃ substrates by a thermal CVD process, by an applied bias voltage between a conducting AFM tip and the films, since I/V characteristics of the device were mainly controlled by the modified gate area in the SFFT. After AFM lithography, the critical current of an YBCO thin film was found to be degraded. Raman lines in the modified YBCO film were observed at 340, 502, and 632 cm⁻¹ in Ar the laser system and 142, 225, and 585 cm⁻¹ in the He-Ne laser system. Raman fluorescence images were also produced by mapping the Raman peaks. A strain image of the peak at 142 cm⁻¹ was most clear, which means that a surface of the YBCO thin film was changed into the YBa₂Cu₃O₆ insulator. AFM nanolithography enables us to fabricate a channel between a source and a drain in SFFT in order to get I/V characteristics.     

含负克尔效应半导体可饱和吸收镜的五镜腔飞秒钛宝石激光器的理论分析

基于半导体可饱和吸收镜(SESAM)的负克尔效应，对含SESAM的五镜腔进行了理论计算和分析.结果表明，由于SESAM的负克尔效应，与没有SESAM的相比，锁模激光器的稳区在上稳区的内边缘有明显扩展，这使得激光器锁模启动的工作点更加靠近直流运转时的稳区边缘，从而获得更大的非线性因子.这说明SESAM的可饱和吸收机理具有锁模自启动效应外，其负克尔效应也有助于锁模的自启动. 关键词： 半导体可饱和吸收镜 负克尔效应 五镜腔