两个原子与双模腔场的多光子相互作用：场和原子的动力学性质

研究一对偶极相互作用原子与双模量子腔场的多光子相互作用，分析场和原子的动力学性质，给出腔模平均光子数和原子反转度时间演化的解析表达式，考察腔模初态、初场强度以及原子间偶极－偶极相互作用的影响。     

双模SU(1,1)相干态场与V型三能级原子相互作用的动力学

研究了关联双模SU(1,1)相干态场与V型三能级原子的相互作用对原子动力学行为的影响及双模场的量子统计性质随时间的演化,证明了在双模SU(1,1)相干态光场作用下,原子的拉比振荡表现出与光场初态为双模压缩真空态或SU(2)相干态时的完全不同的特征。 关键词：     

Kerr介质中耦合V型三能级原子与相干态光场作用场的量子性质

研究了Kerr介质中相干态光场与耦合V型三能级原子相互作用过程中场的量子性质.利用量子光学中光场与原子相互作用的耦合Tavis-Cummings模型,对系统的动力学过程进行了求解.讨论了系统初始状态、失谐量、原子间偶极相互作用强度及Kerr系数对光场量子性质随时间演化的影响.数值计算结果表明:初态中场的平均光子数比较小...     

基于DNA损伤的蛋白调控网络研究

细胞生长的每个阶段都离不开蛋白质相互作用.研究细胞周期的功能、调控机理及参与调控的蛋白质之间的关系对生物工程等领域有重大的应用价值.本文通过研究电离辐射下生物体细胞的DNA损伤后,细胞内以p53为核心的扩展蛋白调控网络的功能、原理及其自修复机理,在现有蛋白网络基础上引入更多蛋白网络调控因子来建立蛋白调控网络,仿真模拟更为全面的细胞周期进程;并且从复杂网络图论和细胞周期调控两个方面分析扩展PMP调控网络的抗扰能力及自修复机理,结果表明:1)蛋白网络在对抗环境中出现的小扰动时具有较强的稳定性.但在面对蓄意攻击时网络的稳定性较差.2)受损的DNA能否被修复取决于p53蛋白的动力学行为,即低损伤与中损伤情况下,p53可诱导细胞周期进程阻滞来完成细胞的自修复;而当高损伤或过损伤时,p53蛋白浓度表现为周期振荡行为并诱导细胞凋亡.     

SeF_n(n=0,+1,+2)基态及SeF低激发态的势能函数与微观性质

为了弄清氟与硒相互拮抗作用的动力学特征,了解SeFn(n=0, 1, 2)分子离子基态和激发态势能函数及微观结构、性质的基本信息是必要的.本文采用6-311 G**基组、B3LYP方法对SeFn(n=0, 1, 2)分子离子基态进行了结构优化和频率计算,用TDB3LYP/6-311 G**含时方法对激发态B12Π、B22Π进行了计算,得到SeFn(n=0, 1, 2)分子离子基态和SeF分子激发态B12Π、B22Π的平衡几何结构、电子状态、谐振频率、偶极矩、离解能De等性质,并在计算出来的一系列单点势能基础上,用正规方程组拟合Murrell-Sorbie(M-S)势能函数,得到相应态的解析势能函数,光谱参数Be、αe、ωe、和ωeχe,由此计算对应的光谱参数和力学性质.理论计算值与相关文献值吻合较好,说明用B3LYP(TDB3LYP)/6-311 G**方法计算SeFn(n=0, 1, 2)分子离子基态和激发态微观结构性质是可行的.     

人工规范势下三阱玻色-爱因斯坦凝聚系统的动力学研究

研究了人工规范势下三阱中的冷原子系统.首先给出了无相互作用的单粒子系统和多粒子系统的能谱性质:在单粒子系统中,随着等效磁场的变化,不同动量的本征态将轮流成为系统的基态;而对于多粒子系统,能级则由粒子数布居决定.在纯量子框架下讨论了系统的动力学演化,发现在排斥相互作用下隧穿和排斥相互作用比值r′_*的从小到大变化可以导致系统从局域到非局域转变,转变的临界点是r′_*=1,以及等效磁场引起的宏观旋转效应.讨论了无相互作用系统各格点粒子数布居的表述曲线（n₂+n₃）-（n₂-n₃）的边界效应,并讨论了相互作用对这一效应的影响.     

光电负反馈下1550nm垂直腔表面发射激光器的动力学特性

基于激光输出的时间序列、功率谱以及相图,对1 550 nm垂直腔表面发射激光器(1 550 nmVCSELs)在光电负反馈作用下的动力学特性进行了研究.结果表明:固定偏置电流,在不同反馈强度下,光电负反馈1 550 nm VCSEL可呈现规则脉冲态、准周期态、混沌脉冲态等非线性动力学态;固定反馈强度,偏置电流取不同值时.1 550 nm-VCSEL也可呈现脉冲态、准周期态、混沌脉冲态等不同的非线性动力学状态.给出了1 550 nm VCSEL非线性动力学状态在偏置电流和反馈强度构成的参量空间分布.分析了激光器的动态演化路径,结果表明:在较小偏置电流和弱光电反馈下,激光器主要工作在稳态:随着偏置电流增加,激光器输出的动力学态通常随反馈强度的增加以规则脉冲态-准周期态-规则脉冲态的方式循环演化到混沌脉冲态;当偏置电流增加到一定值后,激光器输出的动力学态随反馈强度的增加主要以规则脉冲态准周期态混沌脉冲态的方式循环演化.     

轨道Feshbach共振附近类碱土金属原子的杂质态问题

近年来,碱土金属原子和类碱土金属原子体系的研究成为冷原子物理的研究热点之一.特别是最近在~(173)Yb原子中发现的轨道Feshbach共振,使得研究有强相互作用的碱土金属和类碱土金属原子系统成为可能,极大扩展了此类原子体系的研究范围.本文介绍了~(173)Yb费米气体在轨道Feshbach共振附近的杂质态问题.在此问题中,位于~3P0态的杂质原子与处于基态的背景费米海相互作用,并在费米海表面产生分子态或极化子态.本文使用试探波函数的研究方法,首先对分子态和吸引极化子态进行介绍,并重点描述了分子态与吸引极化子态间的转变.其次归纳总结了排斥极化子态的相关性质,如有效质量、衰变率等.然后考虑双费米面情况,介绍在闭通道中引入另外一个费米面对系统产生的影响.最后简要介绍二维~(173)Yb费米气体中的杂质态问题.     

介质腔中场-原子作用系统密度算符间距的演化

利用密度算符间距的概念,关注克尔介质腔中非关联双模相干态光场与V形三能级原子相互作用系统中两子系统(原子和光场)间的信息差异,通过数值计算、图形分析,讨论了不同的原子初始态和克尔效应对系统以及子系统密度算符间距的时间演化特性的影响,结果表明:首先,当不存在克尔介质时,无论原子初始处于哪种状态,系统和原子密度算符间距的振荡均呈现崩塌、复原现象.其次,随着克尔效应的增强,(1)原子初始态为激发态时,系统中原子和光场密度算符间距的演化曲线呈现周期性变化,且克尔效应越强周期性越明显;(2)原子初态为基态时,原子间距的演化曲线逐渐变成一条直线,原子末态几乎不随时间变化,处于稳态,光场间距的演化曲线在不断振荡.最后,激发态和基态原子两种情况下,随着克尔效应的增强,原子间距的值越来越小,即原子末态离初态愈来愈"近",表现了克尔介质的态囚禁效应;光场间距的值增大,即光场末态离初态越来越"远";系统间距的演化曲线保持在1,即在正交态附近振荡.     

多光子Jaynes-Cummings模型的演化

本文研究了任意初态的多光子Jaynes-Cummings模型的一般演化规律.应用到具体问题,讨论了一个二能级原子与相干光场相互作用的双光子Jaynes-Cummings模型的量子统计性质.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.     

A novel methodology for photometric compensation of projection display on patterned screen

We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation.     

Direction-of-arrival estimation using matrix spatial prefiltering approach

An approach to direction-of-arrival （DOA） estimation for multiple narrowband farfield signals is proposed. The technique uses a novel matrix spatial prefiltering approach. Specifically, a matrix filter is designed to spatially filter the incoming data snapshots. The un-wanted components arriving from the stopband angular sectors are attenuated and the desired components from the angular sector of interest pass with minimal distortion. The matrix filter spatially filters the element-space data and the output reserves the element-space data property, which makes it very useful by passing sensor data through a spatial prefilter prior to applying many other array processors to attenuate interferences and improve system performance. Several examples of DOA estimation problem are presented to illustrate the performance of the proposed spatial prefiltering approach. Results of simulation and real data show that the pre-filter can efficiently attenuate the spatial interferences and significantly improve the estimation and resolution capability of DOA estimators at low signal-to-noise ratios for the sources located inside the passband sector. In addition, the use of spatial prefilter makes it possible to estimate DOAs for multiple sources more than the number of the elements of an array.     

Quantum efficiency calibration of opto-electronic detector by means of correlated photons method

A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal.An absolute calibration system of detector quantum efficiency is performed.And its principle and experimental setup are introduced.A continuouswave (CW) ultraviolet (351 nm),diode-pumped,frequency-doubled,and solid-state laser is used to pump BBO crystal.The quantum efficiencies of the photomultiplier at 633,702,and 789 nm are measured respectively.The coincidence peaks are observed using coincidence circuit.Some measurement factors including the filter bandwidth of trigger channel,the detector position alignment and polarization of the pump light are analyzed.The uncertainties of this calibration method are also analyzed,and the relative uncertainties of total calibration are less than 5.8%.The accuracy of this method could be improved in the future.