Modeling of grating assisted standing wave,microresonators for filter applications in integrated optics

A wide, multimode segment of a dielectric optical waveguide, enclosed by Bragg reflectors and evanescently coupled to adjacent port waveguides, can constitute the cavity in an integrated optical microresonator. It turns out that the device can be described adequately in terms of an approximate coupled mode theory model which involves only a few guided modes as basis fields. By reasoning along the coupled mode model, we motivate a simple design strategy for the resonator device. Rigorous two dimensional mode expansion simulations are applied to verify the predictions of the approximate model. The results exemplify the specific spectral response of the standing wave resonators. As refinements we discuss the single resonance of a device with nonsymmetrically detuned Bragg reflectors, and the cascading of two Fabry–Perot cavities, where the coupling across an intermediate shorter grating region establishes a power transfer characteristic that is suitable for an add-drop filter.     

利用场分布计算单腔微波参量

介绍了利用加速管的场分布计算单腔微波参量的一种方法. 在已知耦合腔链各本征模式的谐振频率和电场分布的条件下，可以通过回路方程组求出耦合腔链的单腔频率和腔间耦合系数. 这种方法给加速管设计和调谐带来了很大帮助，在加速腔数目较多或者结构非均匀的条件下尤为有效.     

Cavity mode control in side-coupled periodic waveguides: Theory and experiment

We demonstrate that the modes of coupled cavities created in periodic waveguides can depend critically on the longitudinal shift between the cavities. In the absence of such shift, the modes feature symmetric or antisymmetric profiles, and their frequency splitting generally increases as the cavities are brought closer. We show that the longitudinal shift enables flexible control over the fundamental modes, whose frequency detuning can be reduced down to zero. Our coupled-mode theory analysis reveals an intrinsic link between the mode tuning and the transformation of slow-light dispersion at the photonic band-edge. We illustrate our approach through numerical modeling of cavities created in arrays of dielectric rods, and confirm our predictions with experimental observations.     

The Entanglement Properties Induced by Atoms in Two Separate Cavities Connected by an Optical Fiber

We study the entanglement evolution between two atoms, which are initially entangled with a third atom and trapped in two separated cavities coupled by an optical fiber. We also investigate the temporal evolution in the entanglement between the atom and the local cavity mode. The influence of the state-selective measurement on the atom outside the cavities and the influence of cavity-fiber coupling coefficient on the entanglement are discussed. The results show that the entanglement can be strengthened through the state-selective measurement on the atom outside the cavities. We also find that, by increasing the cavity-fiber coupling coefficient, the atom-atom entanglement is strengthened, but the atom-cavity entanglement is weakened.     

双光子过程耦合腔系统中的纠缠特性

研究了双光子过程原子与耦合腔相互作用系统,给出了系统总激发数等于2时态矢的演化。采用负本征值来描述两个子系统间的纠缠,利用数值计算方法研究了系统中原子与原子间、腔场与腔场间和原子与腔场间的纠缠特性。讨论了腔场间的耦合强度变化对纠缠特性的影响。研究结果表明:随着腔场间耦合的增强,两原子间的纠缠增强,但原子与腔场间和两腔场间的纠缠却减弱。     

Limits of Coherent Addition of Lasers: Simple Estimate

The coherent combining of single mode lasers using coupled cavities is considered. A simple analytical estimate of the number of lasers that can be efficiently combined in such a way is suggested. Such an estimate agrees with simulations and experiments reported recently.     

Energy Levels of Coupled Plasmonic Cavities

We demonstrate the hybridization of the plasmonic modes in directly coupled whispering gallery cavities fabricated on silver films and present the mode patterns and energy levels using cathodoluminescence spectroscopy.Although the energy of the most antisymmetrically coupled modes is higher than that of the corresponding symmetrically coupled ones,the contrary cases happen for small quantum number modes.We attribute the phenomenon to the different surface plasmon polariton paths between the symmetrically and antisymmetrically coupled modes.These results provide an understanding of the resonant properties in coupled plasmonic cavities,which have potential applications in nanophotonic devices.     

Measurement-induced multipartite entanglement for distant four-level atoms in Markovian and non-Markovian environments

In this paper, we propose a scheme for generating multipartite entanglement of distant four-level atoms separately trapped in individual cavities, each of which is coupled to a non-Markovian reservoir. The entanglement of atoms is generated by measuring the photons leaking from cavities. In non-Markovian environments, we derive dynamical evolution of the entanglement and obtain the condition of generating the long-living multipartite maximally entangled state. When the condition is not satisfied, by introducing a time-varying coupling strength, the maximal multipartite entangled state can also be generated.     

Quantum dynamic behaviour in a coupled cavities system

The dynamic behaviour of the two-site coupled cavities model which is doped with ta wo-level system is investigated.The exact dynamic solutions in the general condition are obtained via Laplace transform.The simple analytical solutions are obtained in several particular cases,which demonstrate the clear and simple physical picture for the quantum state transition of the system.In the large detuning or hoppling case,the quantum states transferring between qubits follow a slow periodic oscillation induced by the very weak excitation of the cavity mode.In the large coupling case,the system can be interpreted as two Jaynes-Cummings model subsystems which interact through photon hop between the two cavities.In the case of λ≈△>> g,the quantum states transition of qubits is accompanied by the excitation of the cavity,and the cavity modes have the same dynamic behaviours and the amplitude of probability is equal to 0.25 which does not change with the variation of parameter.     

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.     

The effect of magnetron external-cavity coupling on mode spectrum

A two-port magnetron model is discussed whose opposing cavities are coupled by an external wave channel with a common load. The resonance frequencies of equivalent circuit are calculated and analysis is made of the effect of impedance properties of the load on the mode spectrum, that is, frequency pulling and occurrence of hysteresis instability. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 114–118, September, 2006.     

Polarization and spectral characteristics of anisotropic ring laser cavities with nonideal mirrors

A mathematical model for calculating the polarization and spectral characteristics of eigenmodes of nonplanar ring optical cavities with allowance for the phase anisotropy of oblique-incidence mirrors is described. The results of the numerical modeling and experimental measurements of the characteristics of laser mirrors and mode spectra of practically important four-mirror cavities with a nonplanar symmetric axial contour are compared. It is shown that the proposed mathematical model can be applied to optimal selection of lasers for laser cavities with allowance for their real parameters.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

Self-phase modulation in slow-wave structures: A comparative numerical analysis

Self-phase modulation effects in 1D optical slow-wave structures made of Fabry–Pérot cavities coupled by Distributed Bragg Reflectors (DBRs) are discussed. The nonlinear response of the structure is investigated by a comparative analysis of several numerical methods operating either in time or frequency-domain. Time-domain methods include two Finite-Difference Time-Domain approaches, respectively, optimized to compensate for numerical dispersion and to model nonlinearity at any order. In the frequency-domain an efficient method based on a numerical integration of Maxwell’s equations and an iterative nonlinear extension of the Eigenmode Expansion method are discussed. A Nonlinear Equivalent Circuit of DBRs is also presented as a useful model to reduce computational efforts. Numerical results show that bistable effects and self-pulsing phenomena can occur when either the optical power or the number of coupled cavities of the structure are sufficiently increased.     

衰荡腔复杂模拍效应的实验研究

利用光参量振荡器产生的脉冲光研究了衰荡腔在不同条件下的衰减信号,实验表明,衰荡腔的输出信号会呈现复杂的调制。这些现象,有些可利用在谐振腔本征模理论基础上导出的公式来解释,另外一些可能是由于像散和畸变引起的腔的横膜分裂,从而导致复杂的模拍效应,对实验结果进行了分析和解释。     

Structural, electronic, vibrational, and elastic properties of SWCNTs doped with B and N: an ab initio study

A microscopic model is developed in order to analyse the effects of dissipations on single-photon transport in a coupled cavity array where one of the cavities is coupled to a three-level atom and both cavities and the three-level atom are coupled to an external environment. By employing the quasi-boson approach, the single-photon transmission and reflection amplitudes are found exactly for the Ξ-type, V-type and Λ-type three-level atoms. We focus on the dissipation properties in the case of the Λ-type system. Comparing the dissipative case with the nodissipative one, it can be found that the dissipations of the cavities and the Λ-type three-level atom significantly affect the transmission amplitude of single-photon transport. Whether the atom is in tune with the resonant frequency of the cavity or not, incomplete reflection is mostly caused by atom dissipation near the middle dip of the single-photon transport spectrum, while reduced transmission appears to be mainly controlled by cavity dissipation. Dissipations broaden the line width of the single photon transport spectrum.     

S波段宽带高平均功率速调管输出段的研制

研制了一种用于S波段、7.1%带宽、高平均功率速调管的输出段结构。该结构采用双间隙重叠模耦合腔,利用短槽耦合方式,计算得到耦合槽的尺寸,常规选取两个谐振腔的频率、品质因子及两腔间隙中心之距等参数。根据这些参数加工冷测模型,冷测获得的槽的谐振频率和耦合系数与设计值误差只有2.5%。计算的阻抗矩阵曲线与冷测的相对阻抗曲线趋势基本一致,计算的功率与实际的热测结果均满足峰值输出功率大于1.1 MW、平均输出功率大于22 kW的设计要求。实验结果证明该输出段可达到7.1%的带宽,从而验证了该设计方法的正确性。     

Photonic crystal bends and power splitters based on ring resonators

In this paper, theoretical and numerical analysis of low-loss right angle waveguide bends and T-junctions based on ultra-compact photonic crystal ring resonators (PCRR) is presented. Desirable characteristics are obtained by designing the waveguide bends and T-junctions as low-Q resonant cavities with certain symmetries and small radiation loss. A simple analysis, based on coupled mode theory (CMT) in time, is used to explain the operation principles which agree qualitatively with the numerical results. These structures have high transmission efficiency over a large bandwidth in third communication window. Also effects of changing the ring size on power splitter transmission characteristics are discussed. The perfect transmission and zero reflection conditions are discussed by applying coupled mode theory. Results obtained by the finite difference time domain (FDTD) simulations are consistent with those from the coupled mode theory.