207自泵浦相位共轭中的温度与混沌态

２０７自泵浦相位共轭中的温度与混沌态罗毅（西北大学中国西安７１００６９）吕光爵（美麻州大学洛尔分校Ｍ．Ａ．０１８５４）光折变晶体ＢａＴｉＯ＿３中实验测量了自泵浦相位共轭（ＳＰＰＣ）输出与温度的关系，发现当温度超过８２℃后，自泵浦相位共轭输出出现混沌。...     

(BaSr)TiO_3晶体桥式互泵浦相位共轭器特性的研究

利用（ＢａＳｒ）ＴｉＯ３ 晶体构建桥式互泵浦相位共轭器（ＢＰＣＭ）,研究了ＢＰＣＭ 反射率随互泵浦束的入射角和泵浦比变化的实验规律。通过分析（ＢａＳｒ）ＴｉＯ３ 晶体的ｆａｎｎｉｎｇ 散射特性,利用数值计算求解相应的耦合波方程,得出反射率与互泵浦束的入射角和泵浦比的关系特性,其分析结论与实验结果一致。     

光诱导自泵浦位相共轭输出特性的理论分析

光诱导自泵浦位相共轭输出特性的理论分析陈永兴，邱怡申，吕团孙（福建师范大学物理系福建３５０００７）实验已经观察到利用光诱导自泵浦位相共轭（ＩＳＰＰＣ）现象，它可以使原来处于非自泵浦的信号光产生位相共轭输出。而且当光诱导撤去以后，ＩＳＰＰＣ过程可以是可...     

以半导体激光器为泵源的SPPCM的特性研究

以半导体激光器为泵源的ＳＰＰＣＭ的特性研究康瑾，张治国，吴令安，李健，吴星，傅盘铭（中国科学院物理研究所，北京１０００８０）甘建华，王皓月，张军，汤俊雄，王庆吉（北京大学无线电系，北京１００８７１）有关自泵浦相位共轭镜（ＳＰＰＣＭ）的研制及其应用的研...     

光折变互泵浦位相共轭的暂态行为和振动效应

光折变晶体被两束完全不相干的光束所泵浦是互泵浦位相共轭镜的一大特点，实验上实现各种构型的互泵浦位相共轭镜时，总是力图避免两入射光相干．如果两泵浦光是相干或部分相干的，结果将如何呢？He和Cruz等人对此进行了理论和实验研究．Cru。等人的实验研究结果反映了互相干泵光条件下互泵浦位相共轭镜的静态效应，我们考虑泵浦光相于度变化引起的位相共轭光的暂态行为．实验研究了泵光相干度的突变对桥式构型的互泵浦位相共轭光的影响．实验所使用的两泵浦光来自于同一台无标准具、波长为514．5flm的氩离子激光器．两人射光I1和I2为相干…     

薄片型高效SPPC成镜机制与晶体前（后）向光散射特性的实验研究

薄片型高效ＳＰＰＣ成镜机制与晶体前（后）向光散射特性的实验研究张治国，康瑾，朱镛，姜谦，傅盘铭（中国科学院物理研究所，北京１０００８８）张量，王皓月，汤俊雄，王庆吉（北京大学无线电系，北京１００８７１）在光折变研究领域有关自泵浦相位共轭（ＳＰＰＣ）的...     

自泵浦相位共轭中的温度与混沌态

光折变晶体ＢａＴｉＯ３中实验测量了自泵浦相位共轭输出与温度的关系，发现不发温度超过８２℃后，自泵浦相位共轭输出出现混沌。与已有理论模型的计算机模拟解非常接近，说明在光折变晶体的ＳＰＰＣ中，非随机性混沌行为是温度的函数。     

双相位共轭镜的工作条件参数分析

本文讨论了纯扩散机制的光折变晶体用作单作用区的双相位共轭镜（ＤＰＣＭ）时的阈值耦合强度和允许的输入光强比范围，并与双作用区的情况进行比较后，给出了在输入光强比远离１的条件下，双相位共轭镜的正常工作的条件参数。     

高功率二极管泵浦固体激光谐振腔的进展和分析

对近年来用于高功率二极管泵浦固体激光器的新型光腔，如棒成象非稳腔，近共心非稳腔，折迭腔以及ＳＢＳ相位共轭ＭＯＰＡ系统等进行了深入的分析，并对实现高功率输出和高光束质量的相关技术作了讨论。     

BaTiO3;Ce桥式互泵浦相位共轭镜的研究

本文首次用两台Ｈｅ－Ｎｅ激光器在光折变晶体ＢａＴｉＯ３：Ｃｅ中实现了桥式互泵浦相位共轭，并实验确定了互泵浦光的最佳入射角度。对ＢａＴｉＯ３：Ｃｅ桥式互泵浦相位共轭镜的形成机理作了分析，并对实验的结果和现象进行了讨论。     

采用多像素光子计数器的探测率与虚警率

为了完善多像素光子计数器（MPPC）在激光测距和激光雷达等方面应用的理论基础,对MPPC作为激光测距或激光雷达光探测器的探测率与虚警率进行了系统研究,运用泊松理论提出了基于MPPC的探测率与虚警率模型,推导了相应的解析表达式,并进行了数值分析,发现了一些传统探测器不存在的有趣特性。数值结果显示,利用多像素光子计数器作为激光测距的光接收器时,即使不使用门控（选通）技术,仅仅依靠等效光电子数探测阈值调节技术就可以达到实际应用中激光测距的系统要求。其灵敏度可达到光子量级,并能进行光子数分辨。该模型和结果对于促进MPPC在激光测距和激光雷达方面的应用,实现高灵敏度快速探测有一定的理论和实用价值。     

多像素光子计数器的光子数分辨模型与实验验证

以多像素光子计数器(MPPC)的光电特性与工作原理 为基础,提出了MPPC的短脉冲光子数分辨模型,并分别在忽略与考虑光学串话(OC,optical crosstalk)效应时导出MPPC的短脉冲光响应模型。实验表明,理论模型与实验结果吻合, 且实际的光子数分辨谱对理想 分布的偏离主要是由于OC效应引起的。利用本文模型可以方便而准确地反 演出入射光脉冲的平均光子数信息,快速地判断入射光子数分布是否是预期的统 计分布,并可以推广到具有其他脉冲光子数统计分布的情况,具有一定的普适性。 本文理论模型不仅可用于指导MPPC的设计与优化,而且对MPPC在光 子统计分布的测量、单光子源的表征等弱光探测领域的应用具有较重要的意义。     

基于多像素光子计数器的弱光可见光通信实验系统

可见光通信是一种将照明和通信相结合的新型无线通信技术,但是接收端所采用的传统光电检测器的探测动态范围小、探测效率低,限制着可见光通信的发展。为了进一步提升传输距离和通信速率,本文研究了阵列结构的多像素光子计数器(Multi-pixel Photon Counter, MPPC)在可见光通信中的接收模型。实验采用模拟型输出的MPPC作为接收端进行光电转换,首先在弱光实验条件下搭建了可见光通信实验系统,然后推导了基于理想泊松模型的最大似然检测算法并给出了相应的误码率仿真图。仿真结果表明该算法的误码率性能和传统均值检测算法相比更优。最后通过观察不同传输条件下的眼图研究了阵列结构输出的泊松模型和叠加特性,并用实验数据对算法仿真结果进行了验证。实验表明,在工程应用中阵列结构的MPPC相比传统单光子检测器具有一定的优越性,为后续可见光通信系统设计和优化提供了支撑。      

基于MPPC阵列的三维单光子成像技术研究

三维成像技术在自动驾驶、航空任务、军事领域等都有着广泛的应用,不同技术体制的成像系统有不同的优点,其中基于多像素光子计数器(Multi-Pixel Photon Counter, MPPC)的三维成像技术由于其成像速度快、对极弱光敏感等优势具有广阔的发展潜力。然而,由于MPPC阵列发展不成熟,基于MPPC阵列的弱光三维成像探测水平受到限制。利用日本滨松公司研发的具有32×32规模的MPPC阵列S15013系列二维光子计数图像传感器,开发了一套三维成像系统,传感器的每个像素由12个单光子雪崩二极管并联而成,其总探测像素达到1 K以上。基于该系统,分析了阈值电压、镜头光阑等参数条件对三维成像探测结果的影响,对系统探测灵敏度和精度进行了测试,并针对37 m远模拟目标开展了三维成像探测试验。试验结果表明:在回波光子数约1.98 (光子/像素)的暗弱条件下,目标区域测距精度达到0.268 m,三维结构特征明显,达到了接近单光子成像的探测水平。     

Numerical simulation and experimental study of magnetron-injection guns for powerful short-wave gyrotrons

The results of a numerical simulation and experimental study of magnetron-injection guns forming intense helical electron beams for powerful gyrotrons are compared. Beams of three types—laminar beams, beams with regularly intersecting trajectories and beams with irregularly intersecting (mixed) trajectories are studied. The numerical simulation is performed taking into account the influence of the space charge field. The experimental beam characteristics are measured by the retarding field method. The experimental data agree satisfactorily with the results of the theory if the temperature deformation of the electrode systems is taken into account. It is shown that the best velocity distribution characteristics are realized for guns forming laminar beams and boundary beams (intermediate topology between beams with regularly intersecting trajectories and laminar beams).     

非傍轴双曲正弦高斯光束质量因子M2的研究

在标量光场角谱衍射理论的基础上,应用精确光强定义下的非傍轴标量光束的光强二阶矩理论,计算了非傍轴双曲正弦高斯光束的束腰半径、远场发散角、质量因子,并与傍轴双曲正弦高斯光束的质量因子进行了比较研究。数值计算表明,当双曲正弦高斯光束束腰半径较大时,传统光强定义下的光强二阶矩理论近似成立,傍轴与非傍轴理论计算的光束质量因子变化规律完全相同;束腰半径较小时,傍轴理论计算的结果有较大误差,必须采用精确光强定义下的非傍轴光束质量因子的定义作修正。     

A phase-space beam summation formulation for ultrawide-band radiation

A new discrete phase space Gaussian beam (GB) summation representation for ultrawide-band (UWB) radiation from an aperture source distribution is presented. The formulation is based on the theory of the windowed Fourier transform (WFT) frames, wherein we introduce a novel relation between the frequency and the frame overcompleteness. With this procedure, the discrete lattice of beams that are emitted by the aperture satisfies the main requirement of being frequency independent, so that only a single set of beams needs to be traced through the medium for all the frequencies in the band. It is also shown that a properly tuned class of iso-diffracting (ID) Gaussian-windows provides the "snuggest" frame representation for all frequencies, thus generating stable and localized expansion coefficients. Furthermore, due to the ID property, the resulting GBs propagators are fully described by frequency independent matrices whose calculation in the ambient environment need to be done only once for all frequencies. Consequently, the theory may also be expressed directly in the time-domain as will be presented elsewhere. The localization implied by the new formulation is demonstrated numerically for an UWB focused aperture. It is shown that the algorithm extracts the local radiation properties of the aperture source and enhances only those beams that conform with these properties, i.e., those residing near the phase space Lagrange manifold. Further localization is due to the fact the algorithm accounts only for beams that pass within a few beamwidths vicinity of the observation point. It is thus shown that the total number of beams is much smaller than the Landau Pollak bound on the aperture's degrees of freedom.     

Analysis of Gaussian beam propagation and diffraction by inhomogeneous wave tracking

Inhomogeneous waves behave locally like A(r) exp[ikS(r)], where A and S are spatially dependent complex amplitude and phase functions, and k is the (large) free-space wavenumber. A previously developed asymptotic theory for high-frequency propagation and scattering of such waves is here applied to the propagation and scattering of paraxial Gaussian beams. Attention is given to Gaussian beams in free space, to beams in a lens-like medium with parabolic variation of the refractive index, and to beam reflection by a cylindrical obstacle. In the latter instance, the obstacle size may be comparable to the incident beamwidth, thereby introducing substantial distortion into the reflected beam. The results obtained from the asymptotic theory are verified by comparison with rigorously derived solutions, thereby confirming the validity of the theory, which can also be applied to more general medium and obstacle configurations.     

广义米理论及其在粒度分析中的应用

有形波束的散射问题在粒度分析测量仪器的研究中有着特殊重要的意义，本文介绍了处理均匀球形粒子对有形波束散射的广义米理论，并应用该理论研究了双柱形激光波束粒子测量系统的散射问题，与未理论和几何光学相比，其结果与实验吻合很好。     

Theory of acoustooptical filtration of light beams in the inhomogeneous acoustic field

The theory of acoustooptical (AO) interaction between light beams in the longitudinally inhomogeneous acoustic field is constructed with allowance for conditions typical of AO filtration. In the case of smooth acoustic inhomogeneities, analytical expressions for the spatially spectral characteristic relating the spatial spectra of incident and diffracted light beams are derived. The situation where a Gaussian light beam undergoes filtration in the acoustic field excited by a rectangular transducer is discussed in detail. The narrowband quasi-collinear AO filter based on a paratellurite crystal is simulated. It is demonstrated that the maximum diffraction efficiency and transmission-function shape distortion (with respect to the plane-wave model) of the given device depend to the greatest extent on the misalignment between the directions of the group velocities of interacting light beams.