Numerical solutions of Green''s integral equation for the diffraction of femtosecond laser pulses through a subwavelength aperture

In this letter,we propose a method for the numerical calculations of the femtosecond laser pulse passed through a subwavelength aperture.The time-dependent laser pulse is decomposed into a series of monochromatic simple harmoniv waves.For the light field of the harmonic wave with a single frequency,the numerical calculation is made based on the solution of the Green's integral equation set of the electro-magnetic waves.Such numerical solution is iterated for all the waves with different frequencies,and all thenumerical solutions are transformed into the light fields in the time domain by inverse Fourier transform.The light intensity distributions transmitted the subwavelength aperture are calculated and the resultsshow the propagation of the light field is along the direction of the medium interface.     

金属前驱体比例和硫化温度对Cu-Sn-S薄膜特性的影响

使用射频磁控溅射在镀Mo的玻璃基底上制备了Cu/Sn化学计量比为1.4 ～2.0的金属前驱体薄膜.经过400℃、450℃和500 ℃硫化后获得了一系列Cu-Sn-S薄膜.采用X射线衍射、X射线光电子能谱、拉曼光谱、原子力显微镜和紫外可见近红外分光光度计对样品进行了表征.结果表明:硫化温度与前驱体中Cu/Sn化学计量比对Cu-Sn-S薄膜的结构、化学组分和光学性能影响较大.当硫化温度为450℃,前驱体中Cu/Sn化学计量比为1.4∶1时,能得到近乎单一相、四方结构的Cu2SnS3薄膜,光学带隙为1.01 eV.过高的Cu/Sn化学计量比或硫化温度都会导致Cu3SnS4或Cu4SnS4的出现.     

振荡抽滤-pH计指示电位滴定法快速测定土壤样品中阳离子交换总量

为了提高土壤中阳离子交换量(CEC)分析效率及分析准确度,采用乙酸铵或氯化铵-乙酸铵溶液对土壤样品进行处理,并采用振荡交换、抽滤分离的方式进行离子交换、铵离子清洗。土壤饱和吸附的铵离子用甲醛-CaCl2溶液交换后,采用氢氧化钠溶液滴定,并用pH计准确指示滴定终点,由此测定CEC含量。选用5个国家一级有效态标准物质进行验证,测定值与推荐值相符,相对标准偏差均小于7%,提高了CEC的分析效率与准确度,更加适用于大批量样品的测定。     

强散射体产生的像面散斑对比度与随机表面及成像系统关系的研究

在对4f光学成像系统中强散射体形成的像面散斑的统计特性的研究中, 首先通过散斑场光波复振幅的一般形式和双重指数函数近似求出散斑光强的系综平均, 然后利用散斑场光波复振幅的实部和虚部的旋转变换法求出散斑光强的方差, 最后得出了散斑对比度与随机表面统计参量和系统参量的直接表达式. 本结果与现有文献中包含随机表面相关面积或散射粒子数目的隐含表达式相比具有明显的改进, 并对标定随机表面的散斑对比度法具有重要意义. 关键词： 随机表面 像面散斑 对比度     

Numerical solutions of Green''''s integral equation for the diffraction of femtosecond laser pulses through a subwavelength aperture

In this letter, we propose a method for the numerical calculations of the femtosecond laser pulse passed through a subwavelength aperture. The time-dependent laser pulse is decomposed into a series of monochromatic simple harmonic waves. For the light field of the harmonic wave with a single frequency, the numerical calculation is made based on the solution of the Green's integral equation set of the electromagnetic waves. Such numerical solution is iterated for all the waves with different frequencies, and all the numerical solutions are transformed into the light fields in the time domain by inverse Fourier transform. The light intensity distributions transmitted the subwavelength aperture are calculated and the results show the propagation of the light field is along the direction of the medium interface.     

随机表面散射光场的格林函数法与基尔霍夫近似的比较

从简谐光波满足的亥姆霍兹方程出发，将由格林定理得到的介质分界面上的积分方程转化为以表面上的光波及其导数为未知量的线性方程组，并对其进行数值求解，实现了光场的数值计算. 同时，由透射光场的格林函数积分得出了基尔霍夫近似下光场的表达式. 通过类比推导夫琅和费面上散斑场自相关函数的方法，提出了产生随机表面及其导数的傅里叶变换方法. 在此基础上，对采用基尔霍夫近似进行自仿射分形随机表面的散射光场数值计算的精确程度进行了研究. 发现在随机表面粗糙度比较小时，基尔霍夫近似的精度比较高；在粗糙度相同的情况下，表面的分形 关键词： 格林函数积分 基尔霍夫近似 自仿射分形随机表面