通过改进的受激拉曼绝热通道技术实现多能级系统的布居转移

在受激拉曼绝热过程中,将会出现大量的布居数在中间能级,如果这些能级自发辐射到其他能级,这对于完全布居转移是非常不利的。在本文中我们将提出一种新奇的方法来减少在绝热过程中中间态的布居数。用这种方法,即使中间态自发辐射到其他能级,也能实现完全布居转移。     

偏振纠缠干涉增强理论

采用时间演化算符方法，分析了参量下转换双程系统中纠缠光子的产生和受激放大过程，给出了与实验结果相一致的偏振纠缠干涉增强理论。     

自发吸收原理

依据爱因斯坦关于辐射的量子理论的结论,基于对电磁能量放大现象、受激吸收、自发辐射以及受激辐射的研究,并结合随机电动力学理论,提出并论证了时空量子的受激辐射和自发吸收原理,认为"激发电磁能与自发吸收的时空能之和等于总的电磁能"。     

光子晶体光纤中基于SBS实现慢光的数值模拟

通过运用四阶龙格库塔法和特征线法对基于光子晶体光纤的受激布里渊散射耦合方程组进行数值求解,讨论不同纤芯直径的光子晶体光纤在相同的Stokes波功率和相同的Stokes波强度下对受激布里渊散射慢光产生的影响,发现芯径越小PCF的时延特性越好,但是伴随着较大的脉冲展宽,对于Stokes波脉冲,较小的输入Stokes波功率具有更大的时延.考察不同的脉冲宽度对光子晶体光纤中的慢光的影响,发现较短的脉冲具有更大的相对时延并伴随着较大的脉冲展宽.通过改变小芯径光子晶体光纤的占空比,讨论光子晶体光纤的结构变化对受激布里渊散射慢光的影响,发现小芯径PCF的占空比越小,对应的SBS慢光的时延越大,脉冲展宽也越明显.以上结论可以为慢光缓存器的设计提供理论参考.     

激光

1 激光的产生 分子、原子或离子处于较高能级时可以自动发射一个光子而跃迁到较低能级，这样的辐射称为自发辐射。各个粒子都是独立地发出光子，并向四面，且他们的频率、相位和偏振方向都是彼此无关的，这种光是非相干光，是普通光源所发出的。 光通过物质时，一部分光子将被粒子吸收，使它们跃迁到较高能级频率适当的照射光还可以迫使处于高能级的粒子发射光子而回到低能级，这样发射的光子称为受辐射，它的频率、相位、进行方向和偏振方向都和诱发光子相同，这种光是相干光。当物质中有辐射能时，吸收、自发辐射和受激辐射三种过程同时进…     

光场的相关函数和压缩效应

本文介绍了原子与腔场的非线性相互作用以及受激辐射场的关联函数和压缩效应,讨论了光学相干、光子的聚束与反聚束效应以及光场压缩态中的一些有趣性质。     

CAEP-FEL装置自发辐射和同步辐射分析

在自由电子激光振荡器中，电子在摇摆器产生的自发辐射与在偏转轨道上产生的同步辐射同时存在，自发辐射是与受激辐射密切相关的过程。分析对比了同步辐射与自发辐射的强度和频谱分布，并与实验结果进行了比较。     

锂分子中紫外扩散带受激辐射

本文首次报道了以６２０．０—６６５．０ｕｍ范围内任一波长激光双光子激发模分子或多光子激发锂原子，获得锂分子紫外扩散带受激辐射．文中对有关的辐射特性及激发机制进行了讨论．     

氢中后向anti—Stokes辐射产生机制的分析

分析了在受激Ｒａｍａｎ散射中后向ａｎｔｉ－Ｓｔｏｋｅｓ辐射产生的几种可能性，与氢的实验结果作了比较，进一步支持了氢中后向ａｎｔｉ－Ｓｔｏｋｅｓ辐射来源于受激Ｂｒｉｌｌｏｕｉｎ散射感生的轴向相位失配的四波混顿过程的观点。     

光泵NH3分子远红外激光一条新谱线的发现

光泵ＮＨ_３分子远红外激光一条新谱线的发现秦家银，郑兴世，罗锡璋，林贻堃（中山大学无线电电子学系，广州５１０２７５）关键词光泵远红外激光，放大自发辐射，受激拉曼跃迁分类号Ｏ４３３．５４自１９７０年美籍华裔学者张道源等人首先使用ＣＯ。激光泵浦ＣＨ。Ｆ产...     

Electroluminescent device with reversible switching between red and green emission

Research on new materials for organic electroluminescence has recently focused strongly on phosphorescent emitters, with the aim of increasing the emission efficiency and stability. Here we report the fabrication of a simple electroluminescent device, based on a semiconducting polymer combined with a phosphorescent complex, that shows fully reversible voltage-dependent switching between green and red light emission. The active material is made of a polyphenylenevinylene (PPV) derivative molecularly doped with a homogeneously dispersed dinuclear ruthenium complex, which fulfils the dual roles of triplet emitter and electron transfer mediator. At forward bias (+4 V), the excited state of the ruthenium compound is populated, and the characteristic red emission of the complex is observed. On reversing the bias (-4 V), the lowest excited singlet state of the polymer host is populated, with subsequent emission of green light. The mechanism for the formation of the excited state of the PPV derivative involves the ruthenium dinuclear complex in a stepwise electron transfer process that finally leads to efficient charge recombination reaction on the polymer.     

红外辐射加热过程分析

根据物体对辐射的吸收理论，阐明当光辐射波长与金属氧化物共振吸收波长匹配时，辐射能量将全部被吸收。由一定成分的金属氧化物组成的红外涂料，将产生特定波段的红外辐射，在金属加热过程中红外辐射传递将起着快速加热的作用。     

线光源平板降膜光催化反应器表面光辐照度分布的研究

采用简化的线性光源球面辐射模型,导出了线光源平板降膜光催化反应器液膜表面光辐照度和辐射能通量的计算公式。对表面光辐照度和辐射能通量进行了无因次化理论分析,在反应器面积一定的情况下,计算了不同线光源长度、灯距和反应器长宽比等因素影响下液膜表面的光辐照度分布和光利用率。结果表明:在线光源和平板反应器的诸参变量中,灯距是最敏感的参变量,逐步增大灯距可使光辐照度分布趋于均匀,但光利用率却随之迅速下降,因此需权衡利弊确定合适灯距。比较了实验条件下反应器中部和边缘液膜表面紫外线灯管照射下的光辐照度测量值和光辐照度理论计算值,二者基本相符。     

Molecular emission from single-bubble sonoluminescence

Ultrasound can drive a single gas bubble in water into violent oscillation; as the bubble is compressed periodically, extremely short flashes of light (about 100 ps) are generated with clock-like regularity. This process, known as single-bubble sonoluminescence, gives rise to featureless continuum emission in water (from 200 to 800 nm, with increasing intensity into the ultraviolet). In contrast, the emission of light from clouds of cavitating bubbles at higher acoustic pressures (multi-bubble sonoluminescence) is dominated by atomic and molecular excited-state emission at much lower temperatures. These observations have spurred intense effort to uncover the origin of sonoluminescence and to generalize the conditions necessary for its creation. Here we report a series of polar aprotic liquids that generate very strong single-bubble sonoluminescence, during which emission from molecular excited states is observed. Previously, single-bubble sonoluminescence from liquids other than water has proved extremely elusive. Our results give direct proof of the existence of chemical reactions and the formation of molecular excited states during single-bubble cavitation, and provide a spectroscopic link between single- and multi-bubble sonoluminescence.     

Excited state intramolecular proton transfer fluorescence emission of <Emphasis Type="Italic">o</Emphasis>-hydroxyphenyl-triazine derivatives

o-hydroxyphenyl-triazine derivatives with formyl substituents were surveyed for the excited state intramolecular proton transfer (ESIPT). The occurrence of ESIPT was confirmed by well-separated emission bands for the derivatives. A low energy change from enol to keto in the excited state explains ESIPT for the derivatives.     

The strong cross relaxation of Er3+ and Yb3+ ions in the oxyfluoride glass ceramics

Oxyfluoride glass ceramic is a new up-conversion fluorescent material with the low phonon energy just like fluoride and the good mechanical stability like oxide. In the oxyfluoride glass ceramics co-doped with Er3+ and Yb3+ ions, the red radiation is dominant while it is excited by the violet light. But in the general fluorescent material, the green radiation is dominant because the multi-phonon relaxation occurs step by step. The strong cross relaxation process of Er3+ and Yb3+ ions is mainly responsible for enhancement of the red radiation intensity in the oxyfluoride glass ceramics. The increase of the red radiation intensity of Er3+ ions by the violet light excitation shows that the rare earth ions are doped into fluoride micro-crystals which are planted into oxide host in the oxyfluoride glass ceramics.     

一种新的低成本微电子机械系统微针加工方法

提出了一种新的空心微针阵列加工方法，利用三次同步辐射曝光和显影过程来加工微针．通过无掩膜曝光实现显影腐蚀的侧向扩展，从而获得微针的尖部形状；为克服因同步辐射光源的光束为近似椭圆高斯分布所造成的微针呈椭圆形及微针在各个方向上的强度不均匀问题，采用正交两次曝光方法来补偿同步辐射光源的光束分布不均匀性．这种方法工艺过程非常简单，并且无需任何特殊装置．文中所有实验是在日本立命馆大学的超导压缩存储环同步辐射光源AURORA的第13条线上完成的．实验结果表明，利用这种新方法可以非常方便地加工出高质量的空心微针，实现微针阵列的低成本、批量化制造．     

Experimental observation of electron-hole recollisions

An intense laser field can remove an electron from an atom or molecule and pull the electron into a large-amplitude oscillation in which it repeatedly collides with the charged core it left behind. Such recollisions result in the emission of very energetic photons by means of high-order-harmonic generation, which has been observed in atomic and molecular gases as well as in a bulk crystal. An exciton is an atom-like excitation of a solid in which an electron that is excited from the valence band is bound by the Coulomb interaction to the hole it left behind. It has been predicted that recollisions between electrons and holes in excitons will result in a new phenomenon: high-order-sideband generation. In this process, excitons are created by a weak near-infrared laser of frequency f(NIR). An intense laser field at a much lower frequency, f(THz), then removes the electron from the exciton and causes it to recollide with the resulting hole. New emission is predicted to occur as sidebands of frequency f(NIR)?+?2nf(THz), where n is an integer that can be much greater than one. Here we report the observation of high-order-sideband generation in semiconductor quantum wells. Sidebands are observed up to eighteenth order (+18f(THz), or n = 9). The intensity of the high-order sidebands decays only weakly with increasing sideband order, confirming the non-perturbative nature of the effect. Sidebands are strongest for linearly polarized terahertz radiation and vanish when the terahertz radiation is circularly polarized. Beyond their fundamental scientific significance, our results suggest a new mechanism for the ultrafast modulation of light, which has potential applications in terabit-rate optical communications.