Dynamical hysteresis in a three-level atomic system

We have experimentally investigated dynamical hysteresis behavior by changing the sweeping frequency of the cavity input field in the optical bistability of rubidium atoms (in a three-level atomic-type configuration) inside an optical cavity. The shape, width (or area), and direction of the hysteresis cycle are sensitive functions of the sweeping frequency for such an optical bistable system.     

Calculation of transverse effects in optical bistability using fast Fourier transform techniques

The bistable system consists of a unidirectional ring cavity containing off-resonance saturable two-level atoms. Fourier transform techniques permit an efficient solution of the free-space and medium propagation equations. Dynamic outputs showing critical slowing down and overshoot switching explicitly display the role of diffractive coupling in a bistable device.     

Feedback-controlled nonresonant laser cooling

We present a new approach to nonresonant laser deceleration and cooling of atoms based on their interaction with a bistable optical cavity. The cooling mechanism presents a photonic version of Sisyphus cooling, in which the conservative motion of atoms is interrupted by sudden transitions between two stable states of the cavity mode. The mechanical energy is extracted due to the hysteretic nature of those transitions. The bistable character of the cavity may be achieved by an external feedback loop, or by means of nonlinear intracavity optical elements. In contrast to the conventional cavity cooling, in which atoms experience a viscoustype force, bistable cavity cooling imitates “dry friction” and stops atoms much faster. Based on this novel approach, we explore the prospects of using optical bistability for efficient radiation pressure cooling of micromechanical devices that are modeled as a Fabry-Perot resonator with one fixed and one oscillating mirror. In all cases, analytical results are presented, supported by realistic numerical examples.     

Observation of absorptive optical bistability in a fabry-perot cavity containing multiple atomic beams

Using an arrangement of highly collimated sodium atomic beams in a Fabry-Perot cavity absorptive optical bistability has been observed. The response of the optically bistable system was investigated on a time scale of the order of 100 times the characteristic time of the cavity. Even so a non steady state behaviour of the system was observed. Good qualitative agreement with the two-level atom mean field radiation theory has been obtained.     

Cooling in a bistable optical cavity

We propose a generic approach to nonresonant laser cooling of atoms and molecules in a bistable optical cavity. The method exemplifies a photonic version of Sisyphus cooling, in which the matter-dressed cavity extracts energy from the particles and discharges it to the external field as a result of sudden transitions between two stable states.     

压缩真空注入对光学双稳的影响

研究了注入压缩真空对介质为Ａ－型三能级原子的环形腔的双稳行为的影响。结果表明,压缩真空的注入明显增大了双稳迟滞环。可以注入适当的压缩真空来控制双稳。     

Noticeable positive Doppler effect on optical bistability in an N-type active Raman gain atomic system

We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity.It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region,which has been known as the positive Doppler effect on optical bistability.In addition,we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type.     

Bistability and Entanglement of a Two-Mode Cavity Optomechanical System

We investigate the bistable properties and the entanglement in a two-mode cavity optomechanical system. Our results show that the bistable regime in terms of pumping amplitude can be adjusted by tuning the detunning. Although the two modes of the cavity interact with the same mechanical mode, there is no entanglement between them, while the two modes entangle with the mechanical mode seperately.     

Optical multistability in three-level atoms inside an optical ring cavity

Optical multistability in an optical ring cavity filled with a collection of three-level Lambda-type rubidium atoms has been experimentally demonstrated. The observed multistability is very sensitive to the induced atomic coherence in the system and can evolve from a normal bistable behavior with the change of the coupling field as well as the atomic number density. The underlying mechanism for the formation of such multistability is also discussed.     

Effect of driving laser intensity fluctuations on optical bistability of a system with large permanent-dipole molecules

The statistical properties of an optical bistable system consisting of two-level atoms with large permanent dipole moments contained in a Fabry-Perot cavity are investigated assuming the external laser intensity fluctuations to be the main source of noise. The probability transformation rule is applied to obtain the probability distribution for the transmitted intensity whereas the probability distribution for the incident intensity is assumed to be that of the partially coherent laser light. It turns out that in the optical bistability region two values of fluctuation parameters are possible for a given value of input intensity, which produces interesting hysteresis effects.     

Optical bistability in a three-level semiconductor quantum-well system

Optical bistable behavior in a unidirectional ring cavity (or a Fabry–Pérot cavity) containing a semiconductor quantum well, described as a three-level ladder-type system with similar transition energies, has been studied. The system interacts with a strong driving field which is in two-photon resonance with the intersubband transition and thus simultaneously drives all three levels into phase-locked quantum coherence. The threshold for switching to upper branch of the bistable curve is found to be reduced due to the presence of quantum interference. Such system can be used for making efficient and fast all-optical switching devices. PACS 78.67.De; 42.50.Hz; 78.20.Bh     

Dynamic Equations and Nonlinear Dynamics of Cascade Two-Photon Laser

We derive equations and study nonlinear dynamics of cascade two-photon laser, in which the electromagnetic field in the cavity is driven by coherently prepared three-level atoms and classical field injected into the cavity. The dynamic equations of such a system are derived by using the technique of quantum Langevin operators, and then are studied numerically under different driving conditions. The results show that under certain conditions the cascade two-photon laser can generate chaotic, period doubling, periodic, stable and bistable states. Chaos can be inhibited by atomic populations, atomic coherences, and injected classical field. In addition, no chaos occurs in optical bistability.     

The role of the interactive Kerr effect in two-photon optical multistability

We show that bistable behaviour in a two-photon resonant system within a cavity may be attributed to interactive mode-pulling via the two-photon optical Kerr effect and also to absorptive bleaching (atomic saturation). The interactive Kerr process may be regarded as giving rise to a new category of optical bistability. Moreover, a mechanism for the recently-predicted tristability can be found in terms of simultaneous competition between the interactive Kerr effect and bleaching.     

Adiabatic cavity QED with pairs of atoms

We study the dynamics of a pair of atoms, resonantly interacting with a single mode cavity, in the situation where the atoms enter the cavity with a time delay between them. Using time dependent coupling functions to represent the spatial profile of the mode, we considered the adiabatic limit of the system. Although the time evolution is mostly adiabatic, energy crossings play an important role in the system dynamics. Following from this, entanglement, and a procedure for cavity state teleportation are considered. We examine the behaviour of the system when we introduce decoherence, a finite detuning, and potential asymmetries in the coupling profiles of the atoms.     

Optomechanical Entanglement Between an Ion and an Optical Cavity Field

I study an optomechanical system in which the mechanical motion of a single trapped ion is coupled to a cavity field for the realization of a strongly quantum correlated two-mode system. I show that for large pump intensities the steady state photon number exhibits bistable behaviour. I further analyze the occurrence of normal mode splitting (NMS) due to mixing of the fluctuations of the cavity field and the fluctuations of the ion motion which indicates a coherent energy exchange. I also find that in the parameter regime where NMS exists, the steady state of the system shows continuous variable entanglement. Such a two-mode optomechanical system can be used for the realization of continuous variable quantum information interfaces and networks.     

Optical bistabilities of higher harmonics: Inhomogeneous and transverse effects

The steady state behavior of optical bistable system in a ring cavity with transverse field variations and inhomogeneousely broadened two-level atoms is investigated outside the rotating wave approximation (RWA). Analytical and numerical investigation is presented for different cases of transverse field variations with Lorentzian or Gaussian line widths. When both (transverse and inhomogeneous) features taken into account, the first harmonic output field component outside the RWA exhibits a one-way switching down processes (butterfly OB) or reversed (clockwise) OB behavior, depending on the atomic linewidth shape.     

Bistable behaviour in squeezed vacua: I. Stationary analysis

A time-independent theoretical and numerical analysis of an optical bistable model of two-level atoms in a ring cavity, driven by a coherent field and in contact with a squeezed vacuum field is presented in the two cases of absorptive and dispersive optical bistability (OB). In the former case, a suitable choice of the phase of the squeezed vacuum field reduces the threshold for OB to occur compared with the normal vacuum case. In the latter case, regions of OB are identified as one or two disconnected simple closed curves depending on the cooperation parameter [0pt] : is the maximum possible value of the critical value of C at fixed values of the squeezed vacuum field parameters. Phase switching effects between different (output) states of the system is investigated in detail. In the absorptive case, one- or two-way optical switching is possible depending on [0pt] . We also present results which demonstrate more complicated switching behaviour in the dispersive case. Received 12 March 1999 and Received in final form 20 August 1999     

普适性的光学双稳及激光动力学方程和稳定性分析

本文从慢包络近似的麦克斯韦方程出发,在优质腔极限下,结合腔的边界条件与平均场极限,建立了适用于任何物质的光学双稳系统及相应的激光系统的动力学方程;并通过对方程的线性稳定性分析,得到了一个普适性的失稳判据。 关键词：     

Atoms in an optical cavity: Quantum electrodynamics in confined space

Cavity quantum electrodynamics studies the behaviour of atoms inside a low-loss cavity. The composite atom–cavity system constitutes a new ‘molecule’ with radiative properties which differ radically from those of the individual components. For example, spontaneous emission becomes reversible, the spectrum splits into several peaks and the intensity fluctuations of the light transmitted by this novel ‘molecule’ are below the classical shot noise limit. In terms of practical applications, the system renders possible, first, the detection of single atoms with a high sensitivity and, second, optical bistability for a few atoms and photons only.     

Entanglement evolution of a two-qubit system with decay beyond the rotating-wave approximation

The entanglement property of two identical atoms, initially entangled in Bell states, coupled to a single-mode cavity is considered. Based on the reduced non-perturbative quantum master equation method, the entanglement evolution of the two atoms with decay is investigated beyond the conventional rotating-wave approximation. We show that the counter-rotating wave terms, usually neglected, have a great influence on the disentanglement behaviour of the system. The phenomena of entanglement sudden death and entanglement sudden birth will occur. In addition, we show that the entanglement can be strengthened by introducing the dipole--dipole interaction of the two atoms.