Photorefractive effects for reversible holographic storage of information

Optical storage of information offers great potential for high capacity and speed. A very promising approach to the embodiment of an optical memory is based on volume storage in the form of phase holograms. Attractive storage materials for such a system are electrooptic crystals. The storage mechanism in these materials is based on light induced permanent changes of the refractive index-the photorefractive effect. In this article the physical processes underlying photorefractive hologram recording are outlined, and some of the advantages and limitations of this method are discussed.     

Intrinsic photorefractive effect of LiNbO3

The photorefractive effect of undoped LiNbO₃ crystals of high purity is studied by means of two-photon excitation of picosecond light pulses. We show that two-photon photorefractive recording is accompanied by characteristic changes of the optical absorption and electron spin resonance spectra due to the formation of color centers. The role of these centers for the photorefractive process in discussed.     

相对论性核碰撞中φ介子增强

用强子和弦级联模型LUCIAE系统地研究了相对论性p+p和Pb+Pb碰撞中φ介子产生.在模型框架内实验测得的158AGeV/cPb+Pb碰撞中φ介子产额相对于同能量p+p碰撞的增强现象,依赖于弦发射胶子的集体效应和奇异夸克压低约化两机制,在一定程度内能得到解释.     

在RHIC的极限碎裂和Ф介子产生(英文)

利用强子和串级联模型LUCIAE研究了PHOBOS的极限碎裂等以及在PHIC进行的Au +Au碰撞中带电粒子多重性的经验标度规律 .对介子的产生机制也通过与带电粒子多重性的比较进行类似的研究 .结果似乎表明在串级碎裂模型中带电粒子和介子有共同的产生机制 .还讨论了PHOBOS经验标度规律的模型依赖性 .     

Fluctuations in synchronously mode-locked dye lasers

We present detailed experimental data on random fluctuations of the pulse properties of a cw rhodamine 6G dye laser synchronously pumped by an acousto-optically mode-locked argon ion laser. It is shown that quantitative information about the fluctuations of the energy, the pulse repetition time and the duration of the pulses can be obtained from the power spectrum of the laser intensity which is measured with the use of an electronic spectrum analyser. This method is capable of revealing small, subpicosecond temporal pulse jitter. We show that the dye laser pulses exhibit an absolute r.m.s. jitter of 20 ps which is induced by the pump laser. The relative jitter in a dual system can be less than 1 ps because well defined correlations of the output fluctuations exist when two lasers are pumped by a common source.     

Significance of intra-cavity power density in synchronous mode-locking of CW-dye lasers

It is shown that there is a well-defined relation between the intra-cavity power density and the temporal structure of ultrashort light pulses generated by a synchronously pumped cw dye laser. To obtain pulses of good quality with high output power the beam cross-section in the lasing medium must be large, because the best performance is achieved at low power density.     

Die Synthese von 3β-Acetoxy-24-aza-24-desoxa-xysmalogenin,. Partialsynthetische Versuche in der Reihe der Herzgifte. 12. Mitteilung,

Synthesis of 3β-acetoxy-24-aza-24-desoxa-xymalogenin Starting from the pregnenolone-derivative 1 we report the synthesis of the possibly cardiac-active compound 24-aza-24-desoxa-xysmalogenin 15 .     

Empirical correlation between the superconducting Tc and the Hall constant

It is found that the superconducting transition temperature and the galvano-magnetic Hall constant at room temperature are correlated in a large number of non-transition elements and alloys.     

Mode-locked lasers and ultrashort light pulses

This article reviews some aspects of the generation of very short optical pulses using mode-locked lasers, with the emphasis laid on pulsed laser systems. Active and passive mode-locking is discussed, and the problem of measuring ultrashort light pulses is considered. A survey of some commonly used sources and techniques for the generation of ultrashort light pulses follows. The paper concludes with a short account of limitations in the generation and propagation of these pulses.     

255. Additional bufadienolides from Ch'an Su. Toad venoms. 39

From the toad venom Ch'an Su the bufadienolides 1, 4, 9, 10, 12, 15, 17, 20, 22, 25 and 18 , the latter as diacetate 19 were isolated and their structure elucidated.