有三重态的四能级系统的光学双稳态

对一种有着单重态和三重态的典型的有机物的四能级系统的光学双稳进行了研究。由密度矩阵的速率方程近拟推导出了光学双稳的状态方程。对单重态和三重态吸收或色散情况下的双稳情况用数值解的方法进行了讨论。文中分析了单重态和三重态的合作参数、原子失谐参数和腔失谐参数对双稳的影响。     

Analog simulation of a simple system with state-dependent diffusion

We have constructed an electronic simulator of a simple bistable system driven by noise, whose intensity is determined by the instantaneous value of the coordinate. We observe that the most probable state of the system can be reversed by altering the noise intensity only in the neighborhood of the barrier, an effect pointed out by Landauer many years ago in the context of discussions on entropy-related stability criteria for nonequilibrium systems. We compare detailed measurements on the system with the recent white noise calculations of Landauer and van Kampen. The system also has interesting possibilities for tests of contemporary colored noise theory which we illustrate with an example.     

MCY-1A型脉冲电路实验仪的研发

阐述了MCY-1A型脉冲电路实验仪的设计原理和制作要领。     

Design and applications of discrete mode Fabry-Perot diode lasers

We describe how the multimode spectrum of a Fabry-Perot diode laser can be tailored using a non-periodic patterning of the cavity effective index. The cavity geometry is obtained from the solution of an inverse problem based on a perturbative calculation of the threshold gain of the longitudinal modes of the cavity. Experimental measurements are presented that demonstrate an all-optical memory element based on the injection locking bistability of a two-mode device. We also demonstrate passive harmonic mode-locking of a device designed to support a comb of six modes. Near-transform limited pulsed output with 2 ps pulse duration at 100 GHz repetition rate was obtained. Prospects for the extension of our approach to locking of larger numbers of modes over wider bandwidths are discussed. Similarities between the effective index profiles found in these devices and those of related devices and grating structures are also highlighted.     

（BaSr）TiO3晶体光诱导自泵浦位相共轭的实验研究

对（ＢａＳｒ）ＴｉＯ３晶体中光诱导自泵浦位相共轭现象进行了实验研究。发现诱导自泵浦的输出特性取决于诱导光束强度和信号光的入射条件，并在一定条件下呈现双稳性．作者认为，这是由于诱导光束改变晶体中信号光束Ｆａｎｎｉｎｇ散射强度分布的结果。     

BSO晶体空间光学双稳态

在理论上预言了一种新的参量空间光学双稳态，即以偏置电压为输入参量，Ｂｉ１２ＳｉＯ２０晶体输出的高斯光束远场光斑中心点的光强为输出参量和输入高斯光束功率为常量的一种光学双稳态。并且在实验中分别实现了正偏置和反偏置两种情况下的偏置双稳态。     

The role of physical environment on molecular electromechanical switching

The influences of different physical environments on the thermodynamics associated with one key step in the switching mechanism for a pair of bistable catenanes and a pair of bistable rotaxanes have been investigated systematically. The two bistable catenanes are comprised of a cyclobis(paraquat-p-phenylene) (CBPQT4+) ring, or its diazapyrenium-containing analogue, that are interlocked with a macrocyclic polyether component that incorporates the strong tetrathiafulvalene (TTF) donor unit and the weaker 1,5-dioxynaphthalene (DNP) donor unit. The two bistable rotaxanes are comprised of a CBPQT4+ ring, interlocked with a dumbbell component in which one incorporates TTF and DNP units, whereas the other incorporates a monopyrrolotetrathiafulvalene (MPTTF) donor and a DNP unit. Two consecutive cycles of a variable scan rate cyclic voltammogram (10-1500 mV s(-1)) performed on all of the bistable switches (approximately 1 mM) in MeCN electrolyte solutions (0.1 M tetrabutylammonium hexafluorophosphate) across a range of temperatures (258-303 K) were recorded in a temperature-controlled electrochemical cell. The second cycle showed different intensities of the two features that were observed in the first cycle when the cyclic voltammetry was recorded at fast scan rates and low temperatures. The first oxidation peak increases in intensity, concomitant with a decrease in the intensity of the second oxidation peak. This variation changed systematically with scan rate and temperature and has been assigned to the molecular mechanical movements within the catenanes and rotaxanes of the CBPQT4+ ring from the DNP to the TTF unit. The intensities of each peak were assigned to the populations of each co-conformation, and the scan-rate variation of each population was analyzed to obtain kinetic and thermodynamic data for the movement of the CBPQT4+ ring. The Gibbs free energy of activation at 298 K for the thermally activated movement was calculated to be 16.2 kcal mol(-1) for the rotaxane, and 16.7 and 19.2 kcal mol(-1) for the bipyridinium- and diazapyrenium-based bistable catenanes, respectively. These values differ from those obtained for the shuttling and circumrotational motions of degenerate rotaxanes and catenanes, respectively, indicating that the detailed chemical structure influences the rates of movement. In all cases, when the same bistable compounds were characterized in an electrolyte gel, the molecular mechanical motion slowed down significantly, concomitant with an increase in the activation barriers by more than 2 kcal mol(-1). Irrespective of the environment--solution, self-assembled monolayer or solid-state polymer gel--and of the molecular structure--rotaxane or catenane--a single and generic switching mechanism is observed for all bistable molecules.     

Current oscillations during the electrochemical oxidation of sulfide in the presence of an external resistor

The electrochemical oxidation of sulfide on a polycrystalline platinum electrode was studied under potentiostatic condition when an external resistor is in series with the working electrode. Only two os- cillatory regions can be obtained in the absence of the external resistance, but four oscillatory regions, including two new current oscillations, were found in this system by controlling the external resistance. It is demonstrated that three oscillatory regimes, which arise on the positive branch of current-potential curve, can be classified as HN-NDR (Hidden N-shaped Negative Differential Resistance) oscillators. For the first oscillatory region, various transient complex phenomena, which result from the change of the electrode/electrolyte interface by accumulation of adsorbed element sulfur on the electrode, have been observed. The dynamic behavior of NDR (Negative Differential Resistance) oscillations, appearing along with negative branch of polarization curve, can transform from oscillations into bistability with a sufficient large external resistance in series. Two oscillatory regions in high-potential region classified as HN-NDR type oscillations are separated by a saddle-loop bifurcation. They displayed a sequence of bursting oscillations and irregular oscillations, respectively. The electrochemical oxidation of sulfide provides a model system for studying complex dynamics and possible application in sulfur removal.     

利用腔内四能级原子相干效应实现全光学信号存储

在光学腔与四能级原子组成的非线性光学双稳系统中，利用调谐于不同能级附近的控制信号光脉冲可以使光学腔模产生“IT”或“负”的非线性相移，从而实现了光学双稳迟滞曲线的受控移动及双稳“高态”与“低态”之间的可控跃变，基于上述效应，完成了光学信号的全光存储与腔输出状态的低功率控制开关．这一结果为全光及量子信息处理提供了新的可供利用的物理机制．     

非共振条件下∧型三能级原子系统光学双稳态和多稳态的控制

非共振条件下,我们理论研究了单向环形光腔中用一微波场驱动一个超精细低能态跃迁的∧型三能级原子系统光学双稳态和多稳态行为,结果表明原子介质双稳态的行为可以分别通过耦合场的强度和耦合场频率的失谐量控制,同时还发现微波场在实现多稳态过程中所起的重要作用.最后讨论了合作参数对光学多稳态阈值的影响.