准相位型光子筛设计

提出了一种准相位型光子筛。该准相位型光子筛通过改变暗环上小孔直径与带宽的比值,对焦点处的相位分布进行调制,使通过亮环和暗环上小孔的光波在焦点处发生相长干涉,生成聚焦光斑。该准相位型光子筛无需对基底进行特殊处理,即可完成相位型光子筛的制作,降低了加工难度。和普通振幅型光子筛相比,在相同最小加工尺寸的条件下,准相位型光子筛具有较大的数值孔径,可降低聚焦光斑尺寸。并且,和多区光子筛相比,在同样的最小加工尺寸及数值孔径的条件下,准相位型光子筛光斑尺寸及质量均优于对方。为大数值孔径光子筛设计提供了一种新的设计方法。     

一维新型阶梯函数光子晶体透射特性

研究了阶梯型折射率n22、n11(阶梯分布高度)的大小、对应的分布厚度、不同入射角以及缺陷模对阶梯函数型光子晶体透射特性的影响.由费马原理给出光在函数光子晶体中的运动方程,再由电磁传播理论给出函数光子晶体的传输矩阵,进一步推导出函数光子晶体的透射率以及电场分布的表达式.研究表明,1)随n22,n11大小或者厚度改变,其禁带变宽;2)随光的入射角增加,其禁带变窄;3)当加入缺陷层时,随着缺陷层介质折射率增加,缺陷模强度减小且位置发生红移;4)在函数光子晶体中,缺陷层前电场分布保持不变,而在缺陷层处以及之后的电场强度都明显增强,这不同于常规光子晶体的电场分布仅在缺陷层处局域增强.     

新型闪烁材料——闪烁光纤

本文简要地介绍闪烁光纤的工作原理,指出了掺Tb~(3+)和Ce~(3+)闪烁玻璃光纤的谱特性和衰变时间常数,将它们和CeF_3与其它元机闪烁材料的特性进行了比较,从而得知CeF_3及掺Ce~(3+)闪烁玻璃光纤存在着潜在的巨大应用市场。 The working principle of scintillating fibers is briefly introduced in this paper. Thedecay time constant and spectral properties of the scintillating fibers of Tb_2O_3 and Ce_2O_3 glass aregiven. Comparing the properties of materials above and CeF_3 with those of other inorganic scintillatingmaterials, we find that CeF_3 and scintillating fibers of the Ce_2O_3 have an immense potential applicationmarket.     

Spectroscopic properties of thulium ions in bismuth silicate glass

A new type of bismuth silicate glass (Bi2O3-SiO2-ZnO-Al2O3-La2O3) doped with Tm2O3 is prepared by melt-quenching method. The thermal stability of the glass is examined by differential scanning calorimetry. No crystallization peak is found. Using the absorption and emission spectra, the absorption and emission cross-sections are calculated. Their maximum data are 2.9×10-21cm2 at 1663 nm and 4.7×10-21cm2 at 1826 nm, respectively. Using the Judd-Ofelt theory, the radiation transition probabilities and radiative lifetimes are obtained. The extended overlap integral method is applied to analyze energy transfer process among the Tm3+ ions. The transfer constants of cross-relaxation and energy migration among the Tm3+ ions at the 3H4 level are 7.60×10-40 and 14.98×10-40 cm6 /s, respectively. The critical transfer radius for cross-relaxation is 0.99 nm. The cross relaxation process is easy to realize and is favorable for obtaining ～2-μm laser.     

分离式热管换热器传热特性的实验研究

本文在自行设计分离式热管实验装置的基础上,对其传热特性进行了实验研究。其工作温度为170～250℃,热流密度为25～50 kW/m~2。蒸发段和冷凝段构成相同,均是由7根直径30 mm的无缝钢管短管束组成,管长为160 mm,带有紧套的钢帛环形肋片结构尺寸为:外径45 mm、厚1 mm、片间距4 mm。实验结果表明,在本实验条件下,分离式热管的最佳充液率按管束总容量计为18%～38%。根据实验结果拟合了最佳充液率(24%)下蒸发段内部平均沸腾换热系数和冷凝段内部凝结换热努塞尔数综合关系式。     

电弧放电等离子体诱导激波的计算

基于电弧放电物理过程,分析气动激励机理,建立用于电弧放电等离子体诱导激波数值模拟的爆炸丝传热模型.主要结论有:电弧放电等离子体气动激励的主要机理是热等离子体的热阻塞效应,热电弧放电对于超声速来流而言就像-个具有-定斜坡角度的虚拟突起;理论分析只适用于纵坐标较小的阶段;当传热的功率设为放电功率的10%时,本文所建立的模型能够用于电弧放电等离子体诱导激波的仿真研究;等离子体虚拟斜坡角度及其诱导激波角都随来流总压和速度的增大而减小,随着放电功率的增大而增大,在总压、速度和放电功率较小的阶段这种变化较明显,在总压、速度和放电功率较大的阶段这种变化较缓慢.     

Instrumentation of coherent X-ray imaging and the primary experimental results

Coherent X-ray microscopy has advanced towards higher-energy, more brilliant sources over the past decade since its demonstrations, and many advancements have been made towards optimizing this imaging technique. Here we present both the experimental instrument for obtaining diffraction patterns and the primary reconstruction of yeast cell 2D projection. In addition, the characteristics of the existing optics at BL29XUL of SPring-8 Facility and the method of image reconstruction are discussed.     

Absorption properties of a driven Doppler—broadened ladder system with hyperfine structure

We have studied the absorption spectrum of a Doppler-broadened ladder system,where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field.We find that,when the system is considered as homogeneous,either two or three spectral components are observed,depending on the detuning of the coherent field.but when the velocity distribution of atoms is considered,we can always observe one electromagnetically induced transparency (EIT) window with high dispersion.So the atomic hyperfine structure cannot be an impediment for obtaining EIT.     

Artificial neural network method for determining optical properties from double-integrating-spheres measurements

<正>Accurate measurement of the optical properties of biological tissue is very important for optical diagnosis and therapeutics.An artificial neural network(ANN)-based inverse reconstruction method is introduced to determine the optical properties of turbid media,which is based on the reflectance(R) and transmittance (T) of a thin sample measured by a double-integrating-spheres system.The accuracy and robustness of the method has been validated,and the results show that the root mean square errors(RMSEs) of the absorption coefficientμ_a and scattering coefficientμ'_s reconstruction are less than 0.01 cm~(-1) and 0.02 cm~(-1),respectively.The algorithm is not only very accurate in the case of a lower albedo(~0.33),but also very robust to the noise of R and T especially for theμ'_s reconstruction.     

New Expressions for Dark-Hollow Light Beams

A class of new light beams of dark-hollow beams, named sinusoidal dark-hollow beams, is introduced. The propagation formula for a sinusoidal dark-hollow beam through a paraxial ABCD optical system is derived. The propagation properties of the sinusoidal dark-hollow beam are comparatively studied and illustrated with numerical examples.