光学双稳与混沌实验

借助自主研制的"液晶光电混合型光学双稳与混沌系统"研究了光学双稳态与混沌运动的一般规律.在有反馈的条件下,对于1个入射光强,存在着2个不同的透射光强,并以滞后迴线形式为特征,即系统呈现双稳态.依然在有反馈的条件下,系统的运动状态随着延迟时间的增加,由周期振荡、倍周期分岔演化到混沌,而且,混沌对于初始值具有高度敏感性.     

Deterministic patterns of noise and the control of chaos

Real systems in physics, chemistry and biology are always subject to fluctuations that change qualitatively the systems' dynamics. In particular, rare large fluctuations are responsible for the nucleation at phase transitions, mutations in DNA sequences, protein transport in cells and failure of electronic devices. In many cases of practical interest systems are away from thermal equilibrium, and understanding the fluctuations in such systems is one of the fundamental problems of statistical physics that has challenged researchers for decades. Recent progress in the solution of this problem is closely related to the emerging understanding of patterns of deterministic trajectories underlying non-equilibrium fluctuations. These trajectories correspond to the Hamilton equations of motion written for the asymptotic solution of the Fokker - Planck equation and were often thought of as a mere mathematical abstraction. The possibility of quantitative experiments could not be entertained until the appropriate statistical quantity (prehistory probability distribution) had been introduced. In this paper it is shown how such trajectories can be measured experimentally in a number of systems and how the knowledge of these trajectories can be used to solve long standing problems in the theory of fluctuations and in the control theory.     

Influence of frequency noise on nascent hysteresis in optical bistability

We study the influence of frequency noise on optical bistability in the neighborhood of the critical point where the hysteresis loop appears. We show that when the transmitted field evolves on a faster time scale than that of the noise, the hysteresis loop shifts toward lower values of the incident pumping field.     

Deterministic chaos in entangled eigenstates

We investigate the problem of deterministic chaos in connection with entangled states using the Bohmian formulation of quantum mechanics. We show for a two particle system in a harmonic oscillator potential, that in a case of entanglement and three energy eigen-values the maximum Lyapunov-parameters of a representative ensemble of trajectories for large times develops to a narrow positive distribution, which indicates nearly complete chaotic dynamics. We also present in short results from two time-dependent systems, the anisotropic and the Rabi oscillator.     

Deterministic chaos and natural phenomena

The natural time seriesf ₀ F ₂, F10.7, and AE are analyzed and low-dimensional attractors are found, characterized by the correlation dimension and the lower bound of the Kolmogorov entropy. Sources of noise in natural time series are discussed and the concept of extended systems is introduced and used to explain why the number of data required to calculate the correlation dimension of natural time series is higher than that reported by other authors.     

Transients in optical bistability

In this paper we report on both a theoretical model for the transients in optical bistability in a Fabry-Perot cavity and the corresponding experimental results. An analytical calculation permits to predict the shape of the transient curves and the order of magnitude of their time duration in the case of a slow sweep of the length of the cavity. The experiment, which uses the nonlinearity arising from a two-photon transition in rubidium, yields results in good agreement with the theoretical calculation.Work supported by the D.R.E.T.     

光栅光学双稳态

本文报道了一种光栅光学双稳态装置.利用改变一对对称光栅间相对位移,实现了对透过光强的周期性调制.将这样的系统作为传输部分,分别用He-Ne激光和普通白光完成了光学双稳实验.实验结果与理论分析相符.     

Piezooptical optical bistability

A glass fiber piezooptical optical bistability device is reported.Basing on pho-toelastic and strain effects of single-mode fiber,we have realized piezooptical modulation andperformed experiments of optical bistability.     

Effect of transmission fiber and amplifier noise on optical chaos synchronization

Optical chaos propagation has few constraints peculiar to itself which do not become as significant in conventional nonchaotic optical communication. We have investigated the effects of transmission fiber nonlinearities, dispersion and noise of erbium doped fiber amplifier (EDFA) on chaotic signal synchronization in lumped and distributed configuration. It is found that the effects of fiber dispersion can be easily compensated; however, the effects of fiber nonlinearity on chaos cannot be overdone and must be avoided. Three distinct configurations with different combinations of standard telecommunication fiber, dispersion compensation fiber and lumped and distributed EDF for amplification are analysed. The results are compared in terms of sync diagrams and noise figure. The chaos after propagation through distributed amplification performs better as compared to lumped amplification. Also, a new quantitative measure for the calculation of deviation in sync diagram of chaos is introduced.     

Deterministic chaos in laser with injected signal

Dynamic behaviour of an homogeneously broadened laser with injected signal is analyzed for a model in which the polarization is adiabatically eliminated. Detuning between the atomic resonant frequency, the cavity resonance and the frequency of the external signal is considered. We show that a transition to chaos via intermittency is possible for parameters appropriate for CO₂ lasers.     

Dynamic fluctuations in optical bistability

We present results on the time correlation function of a system undergoing absorptive optical bistability. We first use the Zwanzig-Mori formalism to calculate time correlation functions both near marginal stability points and in the coexistence region. Near marginal stability the theory predicts large deviations from a single exponential form of the correlation function. The truncated continued fraction expansion is shown to become inapplicable close to the coexistence point. The difficulties are due to the presence of long time scales, viz. the very large mean first passage times between the two metastable steady states. When these scales are important we show that the memory kernel relaxation is no longer faster than that of a field fluctuation. An increase in the size of the system increases the disparity of the time scales and thus exacerbates the problems of the projection operator formalism as used here following reference [14].We next present an ansatz for the correlation function incorporating the four major time scales important near coexistence, the two single branch relaxation times and the two mean first passage times for transitions between the stable states. This form of the correlation function avoids the difficulties cited in connection with the use of the projection operator method.     

Self-pulsing in two-cavity optical bistability

We discuss two serially coupled ring cavities which contain media modelled by an ensemble of homogeneously broadened two-state atoms. This system produces pulsed outputs for appropriate CW inputs and values of the cooperativity parameters in the absorptive regime. In particular, self-pulsing occurs when both stable and unstable steady-state output versus input characteristics are everywhere monotomic with positive slope. An analytic requirement for this self-pulsing is obtained in the absorptive case.     

富勒烯分子的光学双稳性

本文采用非线性法布里-珀罗腔的全光光学方法,在C_(60)/C_(70)薄膜中首次观测到双稳开关现象,其开关时间为10ns.     

Fluctuations in multiphoton optical bistability

We show that in multiphoton lasers nonclassical effects are absent, whereas in multiphoton optical bistability the maximum reduction of fluctuations is by a factor of four.     

Recent advances in optical bistability

In this paper, recent advances in optical bistability and gating of semiconductors will be reviewed. Nonlinear mechanisms responsible for switching will be described. The advantages of nonlinear etalons for massive parallelism and current problems in performing such operations will be mentioned.     

Nonsecular terms in optical bistability

We investigate the influence of the nonsecular terms on the optical bistability in a photonic-crystal single-atom laser. The nonsecular terms result in a significant reduction of the bistability threshold. The optical bistability can be controlled by adjusting the parameters of the discontinuity in the photon density of states.     

Plasma induced optical nonlinearities and optical bistability in CdS

The transition from a low density gas of excitons to an electron-hole plasma is connected with strong variations of the optical properties. In this contribution we investigate both the optical nonlinearities produced in CdS by an intense laser beam in the spectral region close to the absorption edge and at the position of the laser itself. In a second part it is shown that the nonlinearities at the photon energy of the incident laser may lead to absorptive and dispersive optical bistability.