Generation of Einstein-Podolsky-Rosen-entangled radiation through an atomic reservoir

We propose a scheme for generating two-mode squeezing in high-Q resonators using a beam of atoms with random arrival times, which acts as a reservoir for the field. The scheme is based on four-wave mixing processes leading to emission into two cavity modes, which are resonant with the Rabi sidebands of the atomic dipole transition, driven by a saturating classical field. At steady state the cavity modes are in an Einstein-Podolsky-Rosen state, whose degree of entanglement is controlled by the intensity and the frequency of the transverse field. This scheme is robust against stochastic fluctuations in the atomic beam, does not require atomic detection nor velocity selection, and can be realized by presently available experimental setups with microwave resonators.     

Coupling and level repulsion in the localized regime: from isolated to quasiextended modes

We study the interaction of Anderson localized states in an open 1D random system by varying the internal structure of the sample. As the frequencies of two states come close, they are transformed into multiply peaked quasiextended modes. Level repulsion is observed experimentally and explained within a model of coupled resonators. The spectral and spatial evolution of the coupled modes is described in terms of the coupling coefficient and Q factors of resonators.     

Computation of the statistical properties of laser light

In this paper a statistical ensemble of laser light is defined. The lasing field is treated as a classical variable, the spontaneous emission is considered phenomenally by using a random function. Special attention is paid to the transverse mode behaviour. To calculate the ensemble elements, an approach based on Fresnel integration has been developed. Theoretical investigations into some stripe stable resonators have been carried out. Some results for the intensity, the mode spectrum, the correlation between transverse modes, the beam quality, and the spectra of the intensity and the output power fluctuation are presented and discussed.     

Dichroic optical waveguides and lasers

The transverse structure of modes in optical waveguides and resonators filled with dichroic media is investigated. Two families of Hermite-Gaussian modes, corresponding to two orthogonal polarizations of radiation, are found for transversely one-dimensional field distributions and for approximating the characteristics of the medium by quadratic functions of the transverse coordinate. Angular selectivity is displayed by extraordinary waves and is manifested in a decrease in the increment of the mode upon an increase in the mode number. With account of the absence of deformation in the lowest mode due to selection, this implies that resonators containing dichroic media (including photon crystals) are promising for reducing the angular divergence of laser beams.     

缓变波导开放谐振腔的理论分析

本文给出了确定任意纵剖面形状的缓变波导开放谐振腔内各模式谐振频率的普遍关系式。探讨了腔内各谐振模式场的纵向分布函数的求解方法。具体地分析了鼓形腔和双圆锥腔,分别推导了这两种开放腔各模式的固有谐振频率公式以及场的纵向分布函数。理论分析与实验结果甚为一致。     

The Evaluation of Dielectric Resonators Containing H2O or D2O as RF Coils for High-Field MR Imaging and Spectroscopy

Electromagnetic resonators consisting of low-loss dielectric material and/or metallic boundaries are widely used in microwave technologies. These dielectric resonators usually have high Q factors and well-defined field distributions. Magnetic resonance imaging was shown as a way of visualizing the magnetic field distribution of the resonant modes of these resonators, if the dielectric body contains NMR sensitive nuclei. Dielectric resonators have also been proposed as RF coils for magnetic resonance experiments. The feasibility of this idea in high-field MR is discussed here. Specifically, the dielectric resonances of cylindrical water columns were characterized at 170.7 MHz (4 T¹H Larmor frequency), and evaluated as NMR transmit and receive coils. The dielectric resonance of a cylindrical volume of D₂O was used to image a hand at 170.7 MHz. This study demonstrated that MRI is an effective way of visualizing the magnetic field in dielectric structures such as a water cylinder, and can potentially be generalized to solid-state dielectric devices. The possible applications of dielectric resonators other than simple cylindrical volumes in MRI and MR solution spectroscopy at high field strengths are also discussed.     

Chaotic dynamos generated by a turbulent flow of liquid sodium

We report the observation of several dynamical regimes of the magnetic field generated by a turbulent flow of liquid sodium (VKS experiment). Stationary dynamos, transitions to relaxation cycles or to intermittent bursts, and random field reversals occur in a fairly small range of parameters. Large scale dynamics of the magnetic field result from the interactions of a few modes. The low dimensional nature of these dynamics is not smeared out by the very strong turbulent fluctuations of the flow.     

Piezoelectric surface excitation and detection of GHz-sound waves using planar structures: Hertzian- and H-slot resonators

We report on experiments with two new kinds of microwave resonators for piezoelectric surface excitation of GHz-sound waves. These resonators consist of planar metal structures simply made by photolithography and especially suitable for the higher frequency range where the usual reentrant cavities can be applied no more due to mechanical fabrication difficulties. Moreover, by choosing an appropriate resonator geometry, an electric excitation field with preferred orientation can be generated which allows to enhance or to supress wanted sound modes simply by turning the crystal relative to the excitation structure into an optimum orientation.Supported by Deutsche Forschungsgemeinschaft     

A quantum photonic dissipative transport theory

In this paper, a quantum transport theory for describing photonic dissipative transport dynamics in nanophotonics is developed. The nanophotonic devices concerned in this paper consist of on-chip all-optical integrated circuits incorporating photonic bandgap waveguides and driven resonators embedded in nanostructured photonic crystals. The photonic transport through waveguides is entirely determined from the exact master equation of the driven resonators, which is obtained by explicitly eliminating all the degrees of freedom of the waveguides (treated as reservoirs). Back-reactions from the reservoirs are fully taken into account. The relation between the driven photonic dynamics and photocurrents is obtained explicitly. The non-Markovian memory structure and quantum decoherence dynamics in photonic transport can then be fully addressed. As an illustration, the theory is utilized to study the transport dynamics of a photonic transistor consisting of a nanocavity coupled to two waveguides in photonic crystals. The controllability of photonic transport through the external driven field is demonstrated.     

光学无源谐振腔的矩阵理论(柱坐标)(Ⅰ)——自洽场矩阵方程

本文讨论了文献中提出的根据标量光波传播矩阵理论的光学无源谐振腔自洽场矩阵方程。提出了对自洽场性质的新认识、元模转换概念和自洽场元模结构分析方法。在普遍情况下,严格证明了上述矩阵方程可截取为有穷阶以求近似解。给出了确定上述有穷阶矩阵方程本征值误差上限的严格公式。还给出了估算由该方程导出的所有结果的计算误差上限的较为方便的公式与方法。本文提出的光学无源谐振腔的矩阵理论较方便于各阶横模,包括那些模损耗相当近于1的高阶横模的计算。作者认为这个理论还应该较适合于复杂谐振腔的分析和计算。由于所用坐标系的关系,本文所提出的理论仅适用于理想轴对称性系统。 关键词：     

Remarkable spectral difference between different polarized modes in four-level two-electron atomic system

The spectral difference between different polarized modes in two-dimensional (2D) four-level two-electron atomic system is investigated by simultaneously solving Maxwell's equations and rate equations of electronic population. A new physical model including pumping dynamics is introduced, and the transitions between the energy levels are governed by coupling rate equations and the Pauli Exclusion Principle. Results indicated that polarized lasing modes have different field pattern, spectral range, and intensity. The photons in TE field are easier to leak from random media than those in TM field. The quality factor of TM modes is larger than that of TE modes and the loss of TM modes to be lower than that of TE modes. The spectral properties in four-level two-electron atomic system are polarization-dependent.     

Entanglement Generation Between Two Mechanical Resonators in Two Optomechanical Cavities

A standard model is suggested to explore correlation features of two spatially separated optomechanical cavities. The cavities are coupled through the photon-hopping process. In particular, we investigate the generation of entanglement between mechanical resonators in the strong coupling regime and the two cavities are assumed to be driven by a coherent laser field. In order to quantify entanglement we use the logarithmic negativity. The analytical solutions are presented for the system in a parameter regime very close to the current experimental results. We show that in the presence of the photon hopping process between the cavities, the two mechanical resonators and the field modes can be entangled. This shows clearly that the entanglement can be transfer via radiation pressure of a photon hopping coupling from the intracavity photon-phonon entanglements to an inter-cavity photon-photon or phonon-phonon entanglement.     

Surface magnetostatic oscillations in elliptical bubble domains

A theory of surface magnetostatic oscillations in magnetic bubble domains with an elliptical cross section is presented. The dependences of the eigenfrequencies of resonant modes on the applied magnetic field are analyzed for a barium hexaferrite sample with allowance made for the change in the domain size due to a variation in the bias magnetic field. The range of frequency tuning in response to a magnetic field ranging from the elliptical instability field to the collapse field is estimated. It is demonstrated that elliptical bubble domains can be used as microminiature resonators operating in the millimeter range.     

Optical microcavities formed by semiconductor microtubes using a bottlelike geometry

We report on the realization of optical microtube resonators with a bottlelike geometry. The measured eigenenergies and the measured axial field distributions of the modes can be described by a straight and intuitive model using an adiabatic separation of the circulating and the axial propagation. The dispersion of the axial mode energies follows a photonic quasi-Schr?dinger equation including a quasipotential which can be determined for the actual geometry of the microtube in a precise and simple way. We show that tailoring the geometry of the microtube bottle resonators enables the realization of a wide variety of mode distributions and dispersion relations.     

Nonlinear optics in spheres: from second harmonic scattering to quasi‐phase matched generation in whispering gallery modes

Over the last fifteen years, a series of theoretical and experimental investigations have demonstrated the usefulness of circular geometries to tailor second‐order nonlinear optical effects. However, until recently, such effects have remained rather weak, calling for their enhancement. In parallel, developments in the field of high quality factor spherical or ring resonators have shown that many different types of light‐matter interactions can be dramatically amplified when light is coupled in the whispering gallery modes of such resonators. In high‐quality spherical micro‐resonators, close to one million interactions can occur between a nonlinear molecule and a circulating light pulse. Recent research on nonlinear optics in spherical geometry is reviewed, from micrometer‐size spheres to whispering gallery mode resonators.     

Experimental observation of left-handed behavior in an array of standard dielectric resonators

We demonstrate that by utilizing displacement currents in simple dielectric resonators instead of conduction currents in metallic split-ring resonators and by additionally exciting the proper modes, left-handed properties can be observed in an array of high dielectric resonators. Theoretical analysis and experimental measurements show that the modes, as well as the subwavelength resonance, play an important role in the origin of the left-handed properties. The proposed implementation of a left-handed metamaterial, based on a purely dielectric configuration, opens the possibility of realizing media at terahertz frequencies since scaling issues and losses, two major drawbacks of metal-based structures, are avoided.     

Surface-roughness-induced contradirectional coupling in ring and disk resonators

Reflections that are due to random surface roughness in periodic structures such as dielectric rings and disks inherently phase match forward- and backward-propagating modes. Small reflections are thus considerably enhanced and may impair the performance of traveling-wave resonators. In addition, such contradirectional coupling leads to a splitting of the resonant peak. These effects are studied analytically.     

Frequency conversion and field pattern rotation in WGM resonator with transient inclusion

An investigation of the transformation of whispering gallery modes (WGM) in circular dielectric resonators due to non-uniform temporal changes of the permittivity is presented. An analytical solution is obtained for the case of an instantaneous refractive index change within a circular inclusion in the resonator. Analytic-numerical analysis of the obtained solution shows conservation of the spatial field distribution and a frequency shift. The possibility of field pattern rotation, dependent on the size and the position of the inclusion, is discussed.     

Coupled-resonator optical waveguides doped with nanocrystals

Microsphere resonators doped with semiconductor nanocrystals are explored as building blocks for coupled-resonator optical waveguides (CROWs). The evolution of individual cavity modes into coherently coupled waveguide modes is studied using polarization-sensitive microphotoluminescence spectroscopy. To demonstrate the formation of multisphere photon states, we use a bent linear array of microresonators and probe the properties of the cavity photon field by the spatially and spectrally resolved measurement of the nanocrystal emission. Photon mode coupling is evidenced by the observed mode splitting and emission intensity distributions along the CROW structure.     

Dispersion of volume relativistic magnetoplasma excitation in a gated two-dimensional electron system

The dispersion of the volume relativistic magnetoplasma mode in a gated GaAs/AlGaAs quantum well is measured using a coupled resonators detection technique. The weakly damped relativistic mode exhibits an unusual zigzag-shaped magnetodispersion dependence dictated by the diagonal component of the resistivity tensor ρ_xx. The plasma excitation easily hybridizes with photon modes due to a large spatial delocalization of its electromagnetic field. The effects of electron density and structure geometry on the excitation spectrum have been investigated.