Monte-Carlo simulation of laser diode sub-Poissonian light generation

When laser diodes are driven by high-impedance electrical sources, the variance of the number of photo-detection events counted over large time durations is less than the average number of events (sub-Poissonian light). This paper presents a Monte-Carlo simulation that keeps track of each level occupancy (0 or 1) in the conduction and valence bands, and of the number of light quanta in the optical cavity. When there is good electron–lattice thermal contact, the electron and hole temperatures remain equal to that of the lattice. In that case, the elementary laser-diode noise theory results are accurately reproduced by the simulation. But when the thermal contact is poor (or, almost equivalently, at high power levels), new effects occur (spectral-hole burning, temperature fluctuations, statistical fluctuations of the optical gain) that are difficult to handle theoretically. Our numerical simulation shows that the frequency domain over which the photo-current spectral density is below the shot-noise level becomes narrower as the optical power increases.     

利用双光子吸收效应测量激光脉冲的相干时间

研究了利用反向泵浦－探测双光子吸收材料的方法来测量脉冲激光的相干时间，并测量量了２３ｐｓ，５３２ｎｍ Ｎｄ：ＹＡＧ激光脉冲的相干时间。实验和理论分析表明，光束相干作用增加了双光子吸收，利用此方法可测量其它脉宽激光的相干时间。     

Finite separable metacyclic 2-groups

A finite separable metacyclic 2-group G can be written as the semidirect product of a cyclic group with another cyclic group. Necessary and sufficient conditions are given for when all other split decompositions of G result in, up to isomorphism, this same semidirect product representation for G.     

Perturbed projections and subgradient projections for the multiple-sets split feasibility problem

We study the multiple-sets split feasibility problem that requires to find a point closest to a family of closed convex sets in one space such that its image under a linear transformation will be closest to another family of closed convex sets in the image space. By casting the problem into an equivalent problem in a suitable product space we are able to present a simultaneous subgradients projections algorithm that generates convergent sequences of iterates in the feasible case. We further derive and analyze a perturbed projection method for the multiple-sets split feasibility problem and, additionally, furnish alternative proofs to two known results.     

HM-J16双光子电子直线加速器

简要叙述了 HM-J1 6加速器的设计思想和设计特点。设计了一台采用射频功率反馈的射线能量范围为 6～ 1 6Me V的双光子电子直线加速器。其最大辐射野为 4 0 cm× 4 0 cm,双光子剂量率均大于3 60 c Gy/ (min·m)。     

Interaction of auto-decayed states in molecule photodissociation processes

Summary The process of molecule photodissociation (PD) in the vicinity of the ionization threshold is studied with direct transitions into the dissociative continuum being accompanied by occupation of pre-dissociative Rydberg and quasi-stationary valence (non-Rydberg) configuration states interacting with each other. Interaction with valence configuration of ≈XY is shown to result in major rearrangement of series of Rydberg resonances (whose width and profile indices turn out to depend greatly on the position of valence configuration levels, their own widths and configuration interaction constant). Possibilities of interference stabilization of individual resonances are shown and conditions for formation of bound states, with continuum serving as the background, are discussed. Calculation of the NO molecule photodissociation spectrum (in the (68600⋎71200) cm⁻¹ region) is given.

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Riassunto Si studia il processo di fotodissociazione delle molecole in vicinanza della soglia di ionizzazione con transizioni dirette nel continuo dissociativo accompagnato dall'occupazione di stati di configurazione di Rydberg pre-dissociativa ed a valenza quasi stazionaria (non di Rydberg) che interagiscono tra di loro. Si mostra che l'interazione con la configurazione di valenza di ≈XY risulta in una maggiore ridisposizione di serie di risonanze di Rydberg (i cui indici di ampiezza e profilo appaiono dipendere in gran parte dalla posizione dei livelli di configurazione di valenza, le loro ampiezze e interazione di configurazione costanti). Si mostrano le possibilità di stabilizzazione d'interferenza di risonanze individuali e si discutono le condizioni per la formazione di stati legati, con il continuo che funge da sfondo. Si dà il calcolo dello spettro di fotodissociazione della molecola di NO (nella regione (68600|71200) cm⁻¹).

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Реэиме Йсследуется процсс фотодиссоциации молекул вблизи порога ионизации в спуае ирямъх переходов в диссциативнъій континуум, которъіе сопобождиіотся заполненим пре-диццоциативнъіх ридберровских и квази-стаіциохарнъих валентнъіх (не-Ридберговских) конфигурагуацоннъіх состояний, которъіе взаимодействуіот друт с друтом. Показъівается, что взаимодействие с валентной конфигурацей ≈XY приводит к перегруппировке ряда Ридбергобских резнансов (у которъх џірина и индексъи профилх сущестбенно завият ояпложения уровней валентной конфигурации, их собственнъіх ширин и конфигурационной постоянной взаимодействия. Ппказывается возможность интерференционной стабилизации индивидуальнных резонансов. Обуждаются условия для образования связанных состояний. Проводится вычисление для спектра фотодиссоциации молекулы NO (в области (68600|71200) см⁻¹).

     

Non-classicality of photon added coherent and thermal radiations

Production and analysis of non-Gaussian radiation fields has evinced a lot of attention recently. Simplest way of generating such non-Gaussians is through adding (subtracting) photons to Gaussian fields. Interestingly, when photons are added to classical Gaussian fields, the resulting states exhibit non-classicality. Two important classical Gaussian radiation fields are coherent and thermal states. Here, we study the non-classical features of such states when photons are added to them. Non-classicality of these states shows up in the negativity of the Wigner function. We also work out the entanglement potential, a recently proposed measure of non-classicality for these states. Our analysis reveals that photon added coherent states are non-classical for all seed beam intensities; their non-classicality increases with the addition of more number of photons. Thermal state exhibits non-classicality at all temperatures, when a photon is added; lower the temperature, higher is their non-classicality.     

"量身定做"单光子波包:在量子网络中控制光子/自旋量子界面

文章简要地介绍了如何在量子网络中控制量子界面动力学以实现静态量子比特和动态量子比特的相互转换．具体言之，该界面由半导体量子点、固体光学微腔以及光学波导管构成，静态及动态比特分别为量子点中的电子自旋和波导管中的单光子波包所携带．界面动力学的控制则是基于对量子点、微腔和波导管耦合系统的量子电动力学的严格求解．据此可实现网络中两个远距离节点间的量子态传输、交换以及确定性的建立量子纠缠等量子操作．上述量子界面亦可用于任意指定波形的单光子源或者单光子探测装置。     

脉冲激发三能级体系半导体量子点的单光子发射效率

研究了脉冲激发下单个半导体量子点中单光子发射的统计特性.在旋转波近似条件下，由系统粒子数演化主方程并结合量子回归理论推导了二阶相关函数的运动方程，利用此方程讨论了二阶相关函数随输入脉冲面积的关系.在窄脉冲宽度的脉冲激发下，单光子的发射概率p和效率η都随着强度的增强而产生振荡.研究表明，采用窄脉冲宽度，当输入脉冲面积在π附近时可以得到较高的单光子发射效率. 关键词： 半导体量子点 单光子发射 三能级系统     

非对称开口六边形谐振单环的微波透射特性

受自然界树型结构的启发，设计了分叉树型微结构单元，用电路板刻蚀技术制作了非对称开口六边形谐振单环及其组合结构.采用计算机模拟和实验研究了单个和多个谐振环在微波段(7—12 GHz)的电磁响应行为.研究结果表明：该结构具有负磁导率特性，开口谐振环几何尺寸影响环的磁谐振频率；两环环间距较小时出现二次谐振；带高级分支的辐射状环列相对于不带分支环列透射峰向低频移动.实验和模拟结果相符. 关键词： 负磁导率 开口谐振环 透射率