多光子光学双稳性的研究

本文给出了描述多光子光学双稳性和多光子激光的统一量子力学模型,得到了多光子光学双稳性和多光子激光的态方程,给出了计算多光子光学双稳住阈值的方法.对势函数进行分析之后,得到了静态稳定性判据和开关特性的物理解释,划分了多光子光学双稳特性曲线上的稳定区域和亚稳定区域,指出多光子光学双稳态实际上是多光于光学稳-亚稳双态.本文还讨论了多光子光学双稳态和多光子激光器中的相变问题.     

光学多稳系统的相变及临界点分类

参照朗道相变理的基本精神,确定光学多稳性系统的相变与临床界现象,揭示了相变的多样性,以及多稳系统通向完全单稳状态态的不同路径。多稳性的级次愈高,相变的式样也就愈多。     

光学双稳性的强迫振动模型

本文提出一个新的光学双稳性模型.基于平均场近似,慢变振幅近似和绝热近似的思想,把光学双稳系统看成一个“黑箱”,类比非线性振动理论,指出不同的光学双稳过程(包括不同的工作物质和不同的腔(F-P腔或环腔)),能用一个恰当的强迫振动方程统一地描述.方程中所包含的都是可测量的宏观参量,使得可能直接用实验拟合,与理论结果进行定量对照.用振动理论的方法,把方程演变成自治方程组,从而方便地得到光学双稳性稳态和动态解的一般形式.并用若干已报道的具体例子验证了这个模型的普适性.     

国外光学与光电子学的新进展(Ⅸ)——光学双稳性

<正> 严格地说,如果一个系统在某一输入值区间中的同一输入光强值上有两个稳态输出光强,那么就称该系统呈光学双稳性。八十年代以来对光学双稳性有了更宽的解释,它包含了某些工作条件下呈现双稳性的非线性光学系统的全部稳态和暂态特性。光学双稳性的专题会议和该题材的教科书都涉及到双稳态系统物理学的许多方面,包括非稳性(在恒定输入下的暂态现象)和光学开关(以光控制光)。     

存在双稳性的激光系统中的临界现象

通过实际事例研究了可能出现光学双稳性的激光系统中的临界现象，并且用平均场理论作详细描述，这里揭示了在作为远离平衡系统的上述激光器中一种更为特殊的临界点，它意味着一级相变与二级相变之间的转变。它十分类似于Ｌａｎｄａｕ（１９３７）在他著名二级（平衡）相变理论中所预见的“第二类相变（线）的临界点”。     

物理系统的稳定性与双稳现象(Ⅰ)

以力学系统（非线性振动），热力学系统（气液相变与铁磁相变）及光学系统中的几种双稳现象为实例，采用初等方法阐明系统的稳定性与双稳的基本原理。     

利用带模型探讨染料环形腔系统的光学双稳特性

利用染料分子带模型，探讨了染料环形腔系统的光学双稳特性，得到光学双稳可在一个比较大的频率范围内实现；其双稳区域是染料分子带结构参数（带宽及偶极分布的Ｌｏｒｅｎｔｚｉａｎ宽度等）的函数． 关键词：     

双反馈光学双稳态

提出了采用双反馈来提高光学双稳系统静态稳定度的方法。理论分析和实验均表明，采用这种方法可命名稳定度获得大幅度提高，非常明显地改善了系统输出的稳定性。     

反馈调QCO_2激光器的光学多稳性与不稳性

本文发现在CO_2激光器的腔内插入一个电光调制器,利用正比于输出光的光电转换信号反馈调节激光器的Q值,可以实现光学双稳性与多稳性.文中建立了描述这一系统的数学模型,它由三个一阶非线性微分方程描述,其稳态模型显示了光学双稳性和多德性特点,理论分析和数值计算都证实了这一结果.     

二维R—N型声光光学双稳态

本文在理论上给出了对二维R-N(喇曼-奈斯)型声光作用的光学双稳系统普遍适用的动态方程,并由此导出了该声光光学双稳系统的稳态解,借助于计算机给出了取(1,0)级作为反馈级次情况下的几个级次输入～输出关系曲线,并对此进行了稳定性分析;在实验上对该理论进行了验证,实验结果与理论相符.     

增强吸收型光双稳临界现象的平均场理论

阐明临界现象（包括两类临界点）与相变的平均场（Ｌａｎｄａｕ）理论同样可以适用于增强吸收型光学双稳性（ＩＡＯＢ）．分析了近期提出的ＩＡＯＢ模型^[９］的动力学特征，在此基础上引入了一种准热力学势。在临界点（第二类）附近，该种势不仅体现出双稳系统中相变的共性，而且也反映了ＩＡＯＢ的特殊性。 关键词：     

Stable spatially localized solutions and holes in optical bistability

We investigate the spatial behavior of the electric field for optical bistability in the good cavity limit. We show that stable spatially localized solutions exist in one and two dimensions. In addition we find that stable one-dimensional hole solutions also arise in this driven non-equilibrium system with dissipation and dispersion thus demonstrating that stable holes are not restricted to dispersive systems, but can emerge in strongly dissipative systems as well. A critical comparison with the properties of stable localized solutions in other driven dissipative systems is also included.     

Geometrical aspects of a generalized statistical mechanics

We discuss here the use of generalized forms of entropy, taken as information measures, to characterize phase transitions and critical behavior in thermodynamic systems. Our study is based on geometric considerations pertaining to the space of parameters that describe statistical mechanics models. The thermodynamics of the system is the focus of attention in this geometric context.     

Dressed mode description of optical bistability

We generalize and simplify the definition of mode variables given in Haken's theory of phase transitions in systems far from thermal equilibrium. The Maxwell-Bloch equations for absorptive optical bistability in a ring cavity are rephrased in such a way that the boundary conditions for the field become a simple periodicity condition in space without retardation in time. From this formulation of the Maxwell-Bloch equations we derive the time evolution equations for the mode variables, which describe the dressed mode dynamics. The coefficients of these equations are analytically evaluated in the limit of small transmittivity of the mirrors. Some applications are indicated.     

Statistical-Mechanical Foundations for a Generalized Thermodynamics of Dissipative Processes

A statistical-mechanical formalism for nonequilibrium systems, namely the nonequilibrium statistical operator method, provides microscopic foundations for a generalized thermodynamics of dissipative processes. This formalism is based on a unifying variational approach that is considered to be encompassed in Jaynes' Predictive Statistical Mechanics and principle of maximization of the statistical-informational entropy. Within the framework of the statistical thermodynamics that follows from the method, we demonstrate the existence of generalized forms of the theorem of minimum (informational) entropy production, the criterion for evolution, and the thermodynamic (in)stability criterion. The formalism is not restricted to local equilibrium but, in principle, to general conditions (its complete domain of validity is not yet fully determined). A H-theorem associated to the formalism is presented in the form of an increase of the informational entropy along the evolution of the system. Some of the results are illustrated in an application to the study of a model for a photoexcited direct-gap semiconductor.     

Critical behavior of extremal Kerr-Newman black holes

The previously suggested existence of second-order phase transitions in a series of Kerr-Newman holes is re-examined in the framework of equilibrium black-hole thermodynamics, to distinguish a true transition from another confusing phenomenon. By adopting a physical interpretation unique to the black-hole thermodynamics, various critical exponents are calculated for one side of the transition which is shown actually very likely to occur at the extremal limit.     

光学双稳性临界点的相变行为

本文详细地讨论了光学双稳性(OB)的临界现象。理论分析主要以忽略量子涨落的Fokker-Plank方程的静态解为基础。结果发现,OB的临界现象可以纳入Landau二级相变理论的框架,并且有关临界指数之间的关系也服从标度律。 关键词：     

Dynamical quantum phase transitions in the dissipative Lipkin-Meshkov-Glick model with proposed realization in optical cavity QED

We present an optical cavity QED configuration that is described by a dissipative version of the Lipkin-Meshkov-Glick model of an infinitely coordinated spin system. This open quantum system exhibits both first- and second-order nonequilibrium quantum phase transitions as a single, effective field parameter is varied. Light emitted from the cavity offers measurable signatures of the critical behavior, including that of the spin-spin entanglement.     

Quantum thermodynamics of nonequilibrium. Onsager reciprocity and dispersion-dissipation relations

A generalized Onsager reciprocity theorem emerges as an exact consequence of the structure of the nonlinear equation of motion of quantum thermodynamics and is valid for all the dissipative nonequilibrium states, close and far from stable thermodynamic equilibrium, of an isolated system composed of a single constituent of matter with a finite-dimensional Hilbert space. In addition, a dispersion-dissipation theorem results in a precise relation between the generalized dissipative conductivity that describes the mutual interrelation between dissipative rates of a pair of observables and the codispersions of the same observables and the generators of the motion. These results are presented together with a review of quantum thermodynamic postulates and general results.     

Coexistence of Stable Limit Cycles in a Generalized Curie–Weiss Model with Dissipation

In this paper, we modify the Langevin dynamics associated to the generalized Curie–Weiss model by introducing noisy and dissipative evolution in the interaction potential. We show that, when a zero-mean Gaussian is taken as single-site distribution, the dynamics in the thermodynamic limit can be described by a finite set of ODEs. Depending on the form of the interaction function, the system can have several phase transitions at different critical temperatures. Because of the dissipation effect, not only the magnetization of the systems displays a self-sustained periodic behavior at sufficiently low temperature, but, in certain regimes, any (finite) number of stable limit cycles can exist. We explore some of these peculiarities with explicit examples.