Effects of Atomic Coherence and Injected Classical Field on Chaotic Dynamics of Non-degenerate Cascade Two-Photon Lasers

Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.     

Effects of Atomic Coherence and Injected Classical Field on Chaotic Dynamics of Non-degenerate Cascade Two-Photon Lasers

Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.     

非锁相Lorenz-Haken方程动力学研究

考虑原子的相干性和经典注入光场，利用随机微分方程给出非锁相条件下的Lorenz-Haken方程，研究失谐量、注入经典光场和原子相干性对非锁相Lorenz-Haken方程动力学特性的影响．在激光运转情形，失谐量造成光场位相的混沌，系统在不同条件下，出现四吸引子、双吸引子及单吸引子混沌状态，且体系的分数维维数较锁相条件下增加．光场失谐量、注入光场和原子相干性可抑制混沌．在双稳态运转下，光场位相为π的偶数倍或奇数倍，使光场稳定于正值和负值，故体系出现对称双稳态对，但无混沌状态． 关键词： 非锁相Lorenz-Haken方程 混沌 原子相干性 注入光场     

关于双光子激光损耗机制的研究

本文利用非相对论量子电动力学理论,分别研究热光场和真空辐射场与级联三能级原子的双光子作用过程,阐明在双光子激光中,原子的热损耗所起的重要作用,损耗过程体现为双光子跃迁损失。并证明忽略热噪声影响的条件,给出产生双光子激光对腔Q值的量级要求。 关键词：     

双光子光学多稳态理论

本文系统地研究了双光子共振作用的光学多稳态理论。在平均场近似下求出的状态方程包含了动态斯塔克效应及弛豫时间参数。指出了在平均场近似下,F-P腔与单向环形腔的状态方程有基本相同的形式。分析了双光子光学多稳态的两种物理机构——克尔效应与饱和吸收效应。在一定条件下这两种效应的共同作用可导致双稳态、双双稳态及三稳态。进一步还给出了区分双稳态、双双稳态及三稳态的判别式。最后还研究了双光子四波混频位相复共轭反射率的双稳态及多稳态。 关键词：     

Preparation of steady-state entanglement via a laser-excited resonant interaction

In this paper we propose a scheme in which two-mode entanglement in a steady state is produced by using two lasers to resonantly drive a single four-level atom embedded inside a two-mode optical cavity.In this scheme,atomic coherence induced by a classical laser plays an important role in the process of preparing the entangled state.With the coupling of a strong control field,direct two-photon transition is generated and the relatively weak pump field induces the parametric interaction between two photons,which makes them entangle with each other.By numerical calculation,we find that the degree of entanglement depends strongly on the Rabi frequencies of the classical laser fields and the cavity losses.     

Two-Photon Micromaser with Initial Atomic Coherence

We investigate the quantum dynamics of a two-photon micromaser pumped by atoms injected in the superposition state of the upper and intermediate levels. We simulate a master equation governing the system by the Monte Carlo wavefunction approach and analyse the steady-state behaviour as a function of the atomic transit time. The atomic coherence can effectively enhance the intensity and sub-Poissonian of the cavity field as compared with the atomic mixture. It is also discovered that the phase of the cavity field can be shifted by adjusting the detuning between the atom and field. This result shows that it is possible to manipulate the phase of the cavity field by detuning, due to atomic coherence.     

Steady-state populations of a driven three-level atom in a broad-band squeezed vacuum

A theoretical study is made of the steady-state populations of a three-level atom in a ladder configuration, driven by a superposition of a monochromatic laser wave with a broad-band squeezed vacuum. The master equation for the system and the atomic Bloch equations are derived. The steady-state populations are calculated numerically and shown graphically as functions of two-photon detuning for various cases of the squeezed vacuum. It is shown that, the atomic populations depend strongly on the relative phase of the driving field and the squeezed vacuum. When the phase matching condition is fulfilled, there will be a strong two-photon resonant absorption from the squeezed vacuum, a characteristic different from absorption of photons from a classical field. Received: 28 May 1997 / Revised and Accepted: 10 December 1997     

带注入信号的双光子激光器的双稳性质

以原子均匀展宽的单模环形双光子激光器为模型,用半经典方法讨论有注入信号的双光子激光器的双稳性质。论证在谐调情况下该系统会出现双稳态,并且对于“好腔”和“坏腔”极限,通过绝热消除描述了双稳性导致的输出光的瞬态行为和滞后循环。发现在低分支是单调地趋向稳态,而在高分支是振荡地趋向稳态;在输出场不连续变化之处出现临界慢化现象。     

Cascade Two-photon Correlated-emission Optical Bistability

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Virtual Photon Effects on Chaos in Generalized Lorenz-Haken Equation

The dynamics of an ensemble of two-level atoms injected into a single-mode cavity is studied in the exact atom-field interaction situation, in which the counter-rotating terms describing the so-called virtual photon processes neglected in the rotating-wave approximation, are considered. The cavity mode is driven by the injected classical field,and the atom is prepared in a coherent superposition of the two levels. We first derive the generalized Lorenz-Haken equation by using the technique of quantum Langevin equation, and then numerically study the dynamics of this equation.We find that the virtual photon processes have strong effects on the dynamics, which can cause the trajectory in phase space of strange attractor spiral around four focus points, and the trajectory is modulated by virtual photon processes.The chaos region in parameter space is now enlarged. It should be stressed that the strange attractor can exist in optical bistability, and whether the atomic coherences and classical field can inhibit chaos depends on the laser frequency.     

Virtual Photon Effects on Chaos in Generalized Lorenz-Haken Equation

The dynamics of an ensemble of two-level atoms injected into a single-mode cavity is studied in the exact atom-field interaction situation, in which the counter-rotating terms describing the so-called virtual photon processes neglected in the rotating-wave approximation, are considered. The cavity mode is driven by the injected classical field,and the atom is prepared in a coherent superposition of the two levels. We first derive the generalized Lorenz-Haken equation by using the technique of quantum Langevin equation, and then numerically study the dynamics of this equation.We find that the virtual photon processes have strong effects on the dynamics, which can cause the trajectory in phase space of strange attractor spiral around four focus points, and the trajectory is modulated by virtual photon processes.The chaos region in parameter space is now enlarged. It should be stressed that the strange attractor can exist in optical bistability, and whether the atomic coherences and classical field can inhibit chaos depends on the laser frequency.     

Control and Transfer of Entanglement between Two Atoms Driven by Classical Fields under Dressed-State Representation

We have studied the dynamics and transfer of the entanglement of the two identical atoms simultaneously interacting with vacuum field by employing the dressed-state representation. The two atoms are driven by classical fields. The influence of the initial entanglement degree of two atoms, the coupling strength between the atom and the classical field and the detuning between the atomic transition frequency and the frequency of classical field on the entanglement and atomic linear entropy is discussed. The initial entanglement of the two atoms can be transferred into the entanglement between the atom and cavity field when the dissipation is neglected. The maximally entangled state between the atoms and cavity field can be obtained under some certain conditions. The time of disentanglement of two atoms can be controlled and manipulated by adjusting the detuning and classical driving fields. Moreover, the larger the cavity decay rate is, the more quickly the entanglement of the two atoms decays.     

STEADY STATE BEHAVIOR OF A THREE-LEVEL ATOM IN A TWO-MODE PARAMETRICALLY DRIVEN CAVITY

We have studied the steady-state behavior of a cascade three-level atom in a two-mode bad cavity which is parametrically driven by a classical field. In the weak field limit, it has been found that the atomic population trapping in the upper-level depends on the cavity photon number not only linearly but also quadratically, and the atomic dipole squeezing can occur.     

Quantum coherence preservation of atom with a classical driving field under non-Markovian environment

The exact dynamics of an open quantum system consisting of one qubit driven by a classical driving field is investigated. Our attention is focused on the influences of single-and two-photon excitations on the dynamics of quantum coherence and quantum entanglement. It is shown that the atomic coherence can be improved or even maintained by the classical driving field, the non-Markovian effect, and the atom-reservoir detuning. The interconversion between the atomic coherence and the atom-reservoir entanglement exists and can be controlled by the appropriate conditions. The conservation of coherence for different partitions is explored, and the dynamics of a system with two-photon excitations is different from the case of single-photon excitation.     

引入量子干涉的双光子共振非简并四波混频

研究了级联四能级系统中双光子共振非简并四波混频(NFWM)由于加入耦合光场而产生的量子干涉效应，发现在强耦合场作用下NFWM频谱呈现AT劈裂，它反映的是两个缀饰态的能级.量子干涉还使NFWM信号被抑制或增强.此方法牵涉到三光子共振，因此可以成为研究原子或分子高激发态的有效光谱学工具. 关键词： 四波混频 量子干涉     

Langevin and generalized Langevin types of spontaneous emission of quantum particles

In the effective Hamiltonian representation, we have obtained a quantum stochastic differential equation of a generalized Langevin type for the evolution operator of an atomic ensemble in a microcavity in an external broadband quantized field and in a nonresonant field of the microcavity. We show that, depending on the number of particles in the atomic ensemble, its dynamics demonstrates both the Langevin and the generalized Langevin types of the two-photon spontaneous decay. In this case, one photon is emitted into the cavity mode, whereas the other photon is emitted into the external broadband electromagnetic field. The Langevin type is determined by a considerable Stark interaction of the atomic ensemble with the broadband photon-free quantized field. We show that, here, the Stark interaction is represented by a quantized Poisson process and, depending on its magnitude (at certain numbers of atoms in the ensemble), the two-photon collective spontaneous emission of microcavity atoms can be completely suppressed. In this case, the two-photon spontaneous emission of the singly excited atomic ensemble is described by the two-level model, while the atom-photon cluster of the microcavity under the described conditions is an artificial two-level quantum particle with a strong Stark interaction.     

Measurement Induced Enhancement of Squeezing in Nondegenerate Two-Photon Jaynes-Cummings Model

Squeezing properties in the nondegenerate two-photon Jaynes-Cummings model are investigated. The effects of direct selective atomic measurement and the application of the classical field followed by atomic measurement are analyzed. Different values of the parameters of the classical field are taken into account. It is found that the field squeezing can be enhanced by measurement.     

Measurement Induced Enhancement of Squeezing in Nondegenerate Two-Photon Jaynes-Cummings Model

Squeezing properties in the nondegenerate two-photon Jaynes-Cummings model are investigated. The effects of direct selective atomic measurement and the application of the classical field followed by atomic measurement are analyzed. Different values of the parameters of the classical field are taken into account. It is found that the field squeezing can be enhanced by measurement.     

Generation of cluster-type entangled squeezed vacuum states

We present a scheme to prepare cluster-type entangled squeezed vacuum states （CTESVS） by considering the two-photon interaction between a two-level atom and a high-quality cavity, driven by a strong classical field. After the realization of simple atomic measurements, the generation of CTESVS in four separate cavities is accomplished within the cavity decay time. In the case of large atom=cavity detuning, the scheme is immune to the effect of atomic spontaneous emission.