微谐振环结构体内太赫兹增强效应

基于严格电磁场理论,给出了微型谐振环形和Fishnet结构体内太赫兹波的严格表达式,并利用电磁场的边界条件分析了太赫兹波在微型谐振环形和Fishnet结构体内空间分布的增强效应。数值模拟结果表明:谐振环金属条附近的电场大于磁场,金属条附近的电场相对其他区域明显要强得多,开口处表现更为突出,太赫兹波在Fishnet结构体内电磁场的峰位处电场和磁场分布关于x对称;电场的极值出现在大十字架的上下四个角,而磁场的极值则出现在小十字架的上下两端点。同时用电磁场传输线理论对该现象作出一定的物理解释。收稿日期:; 修订日期:     

Diode-pumped Q-switched Nd:GdVO4/KTP green laser formed with a flat–flat resonator

A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W, the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns, yielding the highest peak power of 7.44 kW; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz.     

小功率高转速蒸汽透平试验研究和优化

小功率高转速蒸汽透平试验研究和优化邵振麒（同济大学汽车工程系上海２０００９２）关键词：小蒸汽透平，效率，优化１前言回收能量和工业装置的余热及利用太阳能等新能源是节能和环保的重要措施，由此产生的机械能可供发电，气体增压等多种用途。在一些废热量不大且不宜...     

注入离子在无定形固体靶中投影射程分布的统计特性

用基于两体碰撞近似的动态蒙特-卡罗模拟方法和Boltzmann输运方程近似解法,研究注入离子在无定形固体靶中投影射程分布的统计特性.讨论注入物理参数对表征射程统计分布的平均投影射程、分布的标准偏差、偏度和峰度等的影响.计算结果与有关实验数据比较符合得较好. 关键词：     

X-ray spectra induced by slow highly charged Ar q + ions in collision with Nb surface

The X-ray spectra of Nb surface induced by Ar ^q+ (q = 16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar¹⁶⁺ ion was neutralized below the metal surface. The K shell electron of Ar¹⁶⁺ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar¹⁷⁺ is three magnitude orders larger than that of Ar¹⁶⁺. Supported by the National Natural Science Foundation of China (Grant Nos.10774149 and 10405025)     

Experiments and analyses of a new type optical system for computed radiography

A new high-performance laser scanning system is designed. In this system, a scanning arm consisting of a pentagonal prism and a scanning object lens is used to replace the traditional Fθ lens, and a circular imaging plate transmission mechanism is specially designed in order to meet the requirement of the scanning arm. At the same time, the stimulation fluorescence can be obtained by the scanning arm. Some main factors that influence the spatial resolution and the performance of the laser scanner system are analyzed, and the analysis results are presented, which is helpful for further optimization design of the system. Experimental results indicate that the images obtained by the system have good visual effects and can meet the requirements of industrial inspection.     

Improving the precision of fluorescence lifetime measurement using a streak camera

Streak camera has high temporal resolution and high sensitivity, and is a powerful tool in biomedical study to measure fluorescence lifetime and perform fluorescence lifetime imaging. However, nonuniformity of the gain in the streak tube and nonlinearity of the sweeping speed limit the precision of fluorescence lifetime measurement, particularly when fluorescence lifetimes are short. We have constructed a two-photon excitation fluorescence lifetime measurement system that is based on a synchroscan streak camera and have developed accordingly a method to correct the effect of gain nonuniformity and nonlinearity of sweeping speed on the measurement precision. A continuous-wave laser of high stability is used to calibrate the gain of the streak camera, and a Fabry-Perot etalon is used to calibrate the nonlinearity of the sweeping speed. Fitting algorithms are used to correct the gain of the streak camera and nonlinearity of the sweeping speed respectively, which significantly improves the measurement precision of the system, as characterized through the fluorescence lifetime of the short-lived fluorescence dye, Rose Bengal. Experimental results show that the measurement fluctuation of the lifetime has been improved from more than 10% to 2% after correcting the effects of gain nonuniformity and sweeping speed nonlinearity.     

Single-material guided-mode resonance filter for TE waves under normal incidence

<正>A guided-mode resonance(GMR) filter with the same material(Ta_2O_5) for both the grating layer and the waveguide layer is designed and fabricated.This simple structure is easy to fabricate and can avoid the defects at the grating/waveguide interface using different materials.The spectral response measured with a Lambda 900 spectrophotometer under normal incidence for TE waves exhibits a peak reflectance exceeding 80%at the wavelength of 1040 nm with a full-width half-maximum(FWHM) linewidth of 23 nm.We evaluate the deviations of the fabricated structure from the designed parameters.     

Theoretical studies on the optical absorption coefficients and refractive index changes in parabolic quantum dots in the presence of electric and magnetic fields

The optical absorption coefficients and the changes in the refractive index in GaAs/AlGaAs parabolic quantum dots(QDs) with applied electric and magnetic fields are studied in detail. Analytical expressions for the linear and nonlinear intersubband absorption coefficients and refractive index changes are obtained by using a compact density matrix approach and an iterative procedure. Finally, the calculated results show the incident optical intensity, the frequencies of the confined potential of the QDs and the applied electric and magnetic fields have a great influence on the optical absorption coefficients and refractive index changes in this system.