Theory of two-photon lasers III

We treat the semiclassical equations and the Fokker-Planck equation of a two-photon laser with one or two injected signals and treat both the degenerate and nondegenerate case. The resulting behaviour in the two-photon laser is discussed by means of potential functions which allows one to determine the stable, unstable, and metastable states.     

Generation of nonclassical states by nonlinear optical systems

We review the main results obtained recently by our group in the field of quantum noise reduction in nonlinear optical systems. We illustrate the possibility of obtaining significant effects in degenerate parametric oscillators, intracavity second-harmonic generation, nondegenerate four-wave mixing, and one- and two-photon optical bistability.     

Measurements of dynamics of nondegenerate optical nonlinearity in ZnS with pulses from optical parameter generation

We expand the degenerate PO pump-probe technique to nondegenerate field and use it to investigate optical nonlinear dynamics in ZnS single crystal. Excited by 532-nm laser pulses with 21-ps duration, the temporal response of nondegenerate nonlinear absorption and nondegenerate nonlinear refraction are probed by laser pulses from optical parameter generation (OPG) at 600 and 680 nm with pulse width of 10 ps. Based on the theory of free-carrier optical nonlinearity, we study the pure free-carrier refraction in ZnS. By numerically fitting based on the nondegenerate pump-probe theory, the nondegenerate two-photon absorption coefficient, the free-carrier lifetime, the free-carrier absorptive cross section and refractive coefficient at both probe wavelengths are determined respectively. The dispersion of the free-carrier refractive coefficients is discussed.     

Complete control of population transfer between clusters of degenerate states

We present an analytic solution to the "degenerate quantum control problem," which enables the transfer of any desired fraction of population between arbitrary initial and final pure wave packets, made up of nearly degenerate energy eigenstates. It consists of two two-photon adiabatic passage steps, in which the population of the initial wave packet is first transferred, via a number of nondegenerate intermediate states, to a single eigenstate and then returned to a different target superposition state. We demonstrate the approach by executing a stepwise isomerization of three Jahn-Teller states of the Al3O molecule, where a proper optical coupling can easily be established.     

Coherent Phase Control of Ultrafast Polarization Beats in Reverse V-Type Three-Level System

We investigate the third-order nonlinear absorption and dispersion of femto- and atto-second polarization beats between the one-photon degenerate four-wave mixing process and the two-photon nondegenerate four-wave mixing process in the pure homogeneously-broadened reverse V-three-level using twin noisy fields. The third-order nonlinear response can be controlled and modified by the colour-locked correlation of twin noisy fields. Most importantly, the coherent phase control in optical heterodyne detection for studying the phase dispersion of the third-order susceptibility is demonstrated. The radiation-matter detuning oscillation is also considered in the freauencv domain.     

阿秒和频相位共轭极化拍频的不对称色锁二阶相干控制

研究了级联三能级系统中孪生色锁随机光场的相位共轭阿秒和频极化拍频(ASPB)不对称新效应。从理论上分析了自关联单光子简并四波混频(DFWM)和双光子非简并四波混频(NDFWM)信号辐射场与物质间不对等效应、混合型太赫兹失谐振荡特性,及双光子非简并共振四波混频信号的延时不对称性;同时也分析了由干涉计两臂不平衡色散效应引起的阿秒和频极化拍频信号的延时不对称性,即阿秒和频极化拍频信号的最大值相对于零延时有一个小偏移,结果表明该不对称性并这不影响阿秒和频极化拍频零差探测两偶极禁戒跃迁能级分裂的总体精度。阿秒和频极化拍频作为一种消除多普勒增宽的超快调制过程,从理论上说它可以扩展到任何两偶极禁戒跃迁能级系统。     

等离子体四波混频透射放大理论

研究了寻常波在磁化等离子体中四波混频透射放大理论，得到了简并和非简并时的精确解析解，其结果适用于非磁化等离子体中的电磁波四波混频． 关键词：     

光子晶体光纤模式的简并特性研究

应用光子晶体光纤（PCF）的全矢量模型，根据对称性分析，按照最小波导扇面及相应的边界条件，将PCF中的模式进行了分类，并将PCF中的模式类比阶跃光纤来命名. 分析表明，PCF中的模式或者为非简并的，此时能够反映波导结构对称性；或者为简并对，必须二者组合才反映波导结构的对称性. 当简并对中的两个模式都具有与PCF波导结构相同的对称性时，简并将被击破而形成两个非简并模. 关键词： 光子晶体光纤 模式 简并     

Degenerate quantum codes for Pauli channels

A striking feature of quantum error correcting codes is that they can sometimes be used to correct more errors than they can uniquely identify. Such degenerate codes have long been known, but have remained poorly understood. We provide a heuristic for designing degenerate quantum codes for high noise rates, which is applied to generate codes that can be used to communicate over almost any Pauli channel at rates that are impossible for a nondegenerate code. The gap between nondegenerate and degenerate code performance is quite large, in contrast to the tiny magnitude of the only previous demonstration of this effect. We also identify a channel for which none of our codes outperform the best nondegenerate code and show that it is nevertheless quite unlike any channel for which nondegenerate codes are known to be optimal.     

高Q Kerr介质腔中非简并双光子Jaynes-Cummings模型中光场的性质

研究了一位于高Q Kerr介质腔中的二能级原子与双模光场相互作用系统中,Kerr效应对光场单模平均光子数、单模二阶相干度、两模间的相关性,以及Cauchy-Schwartz不等式的影响。 关键词：     

The mechanisms for optical bistability in a two-photon resonant system

The categories of optical bistability within a nondegenerate two-beam, two-photon resonant system are presented and discussed.     

Theory of two-photon lasers I

We start from the microscopic Hamiltonian formulated by means of creation and annihilation operators for the field modes, and creation and annihilation operators for the electrons. The virtual transitions via the intermediate atomic level are eliminated by second order perturbation theory so that an effective Hamiltonian results which describes two-photon creation or annihilation. In the next step Heisenberg equations of motion are derived for the field amplitudes, the atomic dipole moments, and the inversion. The effect of heatbaths is taken into account by means of damping terms and fluctuating forces. In the present paper these equations are averaged over the fluctuating forces and the resulting semiclassical equations are solved for the stationary state. We treat the degenerate and nondegenerate case including detuning and atomic levels with homogeneous and inhomogeneous broadening. The field modes may be either running or standing waves. A detailed discussion of the laser condition is given.     

利用费曼路径积分理论分析多光子干涉

将费曼路径积分理论引入量子力学教学,用来分析光子干涉现象.对非简并的两光子和三光子干涉的关联函数进行了推导,并对干涉结果进行了模拟.模拟结果显示,非简并的多光子干涉是多光子聚束和量子拍效应叠加的结果.     

Thermodynamic functions of electron gas on the semiconductor nanotube surface in a magnetic field

Thermodynamic functions have been calculated in the effective mass approximation for degenerate and nondegenerate electron gases on the semiconductor cylindrical nanotube surface in a longitudinal magnetic field. The Laplace transform linking the density of states and the statistical sum has been used. The thermodynamic quantities of degenerate electron gas undergo the de Haas-van Alphen oscillations with the electron Fermi energy change and the Aharonov-Bohm oscillations with the magnetic flux change within the semiconductor tube cross section. The quantities related to nondegenerate gas oscillate only with the change of magnetic flux. A peak has been found in the nondegenerate gas heat capacity-temperature diagram. A limiting process to 2D electron gas on plane has been carried out.     

Quantum Theory of a Nondegenerate Two-Photon Laser

Laser actions and photon statistics far a nondegenerate two-photon laser in an effective three-level stomic system with arbitrary detunlng are Investigated both semiclassically and quantum meehmleally, Due to the two-photon effect, the radiation field easily displays a sub-Foissonian statlstieal distribution. The laser actions for a two-photon and a sihgle-photon loss mechanisms are compared. It is found that the detailed balance in the single-photon loss mechanism can still be preserved in the case that a first-order phase transtion takes place.     

ac Stark effect for a two-level atom in a squeezed vacuum via a two-photon process

The nondegenerate two-photon interaction of a two-level atom with a broadband multimode squeezed vacuum is investigated. We find that in the two-photon process the squeezed vacuum has a driving effect on the atom which can lead to an ac Stark effect when the average photon number of the squeezed vacuum is larger than a critical value. Received: 2 February 1999 / Received in final form: 20 April 1999     

Multidimensional Gaussian probability density and its applications in the degenerate case

We obtain an analytical expression for the probability density of the Gaussian vector with a degenerate covariance matrix. The expression generalizes a similar expression for the nondegenerate case. A definition of the Gaussian vector on the basis of a probability density, which is common for the degenerate and nondegenerate cases, is given. Examples of using the obtained probability density for the synthesis of optimal signal-processing algorithms are presented. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 7, pp. 626–634, July 2006.     

附加克尔介质简并双光子J-C模型的动力学特性

本文利用密度算符间的距离研究了附加克尔介质简并双光子Jaynes－Cummings模型（JCM）的动力学特性．在与标准简并双光子Jaynes－Cummiungs模型以及附加克尔介质单光子Jaynes－Cummings模型相比较的基础上，详细讨论了克尔介质非线性相互作用对该模型动力学行为的影响．     

Linear and nonlinear excitations in warm dense matter

Small and large amplitude linear and nonlinear ion acoustic and Langmuir waves are investigated for plasma with the generalized equation of state (EoS). This EoS covers a wide range of energy-density conditions from dilute classical regime up to the relativistically degenerate matter. Investigation shows that the linear dispersion and localized excitations of ion acoustic waves are significantly affected by the plasma parameters. It is also found that the criterion for ordinary soliton existence is significantly different for fully degenerate and nondegenerate plasma regimes with given electron temperature. In the nondegenerate regime, bright solitons form only for Mach numbers above a critical value which is only a function of the fluid temperature.     

非简并双光子微脉塞的发射几率

将简并双光子微脉塞的量子理论推广到非简并情形, 给出了原子发射几率的解析表达式并且分析了相应的性质.发现由于在微脉塞中存在两种腔场模式,导致有两个自由度来改变原子在经过腔场时所受到的势场,因此非简并双光子微脉塞的发射几率的行为不同于简并双光子情况下的发射几率.