Optical interaction in a plasmonic metallic particle chain coupled to a metallic film

We study the coupling of localized surface plasmon and surface plasmon polariton modes in a system composed of a metallic nanoparticle chain imbedded in a dielectric–metal–dielectric substrate. The results show the influence of outside parts and imbedded parts of particles on the interaction between localized surface plasmon and surface plasmon polariton modes. An enhancement can be observed in our structure. This kind of the structure has a very promising candidate for biosensing and surface enhanced spectroscopy applications.     

Mechanism for designing metallic metamaterials with a high index of refraction

We introduce a mechanism for creating artificial high refractive index metamaterials by exploiting the existence of subwavelength propagating modes in metallic systems. As an example, we investigate analytically and numerically metal films with a periodic arrangement of cut-through slits. Because of the presence of TEM modes in the slits, for TM polarization such a system can be rigorously mapped into a high refractive index dielectric slab when the features are smaller than the wavelength of light. The effective refractive index is entirely controlled by the geometry of the metal films, is positive, frequency independent, and can be made arbitrarily large.     

Effect of a plasma grating on pump-probe experiments near the ionization threshold in gases

Calculations are performed of the phase shift caused by the spatial modulation in the plasma density due to interference between a strong pump pulse and a weak probe pulse. It is suggested that a recent experiment [Opt. Express 17, 13429 (2009)] observed an effective birefringence from this plasma grating rather than from the higher-order Kerr effect.     

Theoretical studies of excitation dynamics in a peridinin-chlorophyll-protein coupled to a metallic nanoparticle

In this work we study the influence of plasmon excitations on the excitation dynamics within a protein complex embedding two chlorophyll molecules coupled to a gold nanosphere. Small separation between the chlorophylls and metallic nanoparticle allows us to simplify the calculations of the Förster energy transfer rate and non-radiative processes by replacing a spherical nanoparticle with a metallic surface. Our results show modifications of all relevant processes and the energy transfer pathways within the system as well as the radiative processes. Plasmon induced changes result in strong qualitative effects of the fluorescence of the studied light-harvesting complex.     

Multi-state optical flip-flop memory based on ring lasers coupled through the same gain medium

We investigate a system consisting of multiple ring lasers coupled by a single gain medium. All the ring lasers share a common feedback arm. The output power of an individual laser shows periodic oscillations as a function of time. The periodicity of the oscillation is determined by the ratio of the roundtrip times of the feedback arm and the ring cavity. In the case that two of such ring lasers are coupled, either their oscillation periodicities are synchronized, or the system is bi-stable. In the latter operation regime, the system can act as an optical flip-flop memory whose state be switched by injection of external light. The concept can be extended to multi-state operations; an eight-state optical flip-flop memory is experimentally demonstrated.     

电磁编码超材料的理论与应用

本文系统地对编码超材料、数字超材料及现场可编程超材料的新进展进行了综述,讨论其对电磁波的实时调控和构造多功能器件的能力。首先,引入1-bit编码超材料,由"0"和"1"两种编码单元构成,分别对应于相位相反的电磁响应。通过控制不同的"0"和"1"编码序列,可以调控电磁波,并实现不同功能。这种1-bit编码超材料可以扩展到2-bit,甚至更高比特。其次,介绍了一种由开关二极管来控制的数字编码超材料,每个编码单元可通过二极管的开和关来获得不同的相位响应,进而获得不同的数字态。结合现场可编程门阵列(FPGA)控制系统,实现了对数字超材料的实时可编程设计,构造出现场可编程超材料。最后,研究了编码超材料对太赫兹波的调控,包括太赫兹波宽带漫散射及其对目标雷达散射截面(RCS)的缩减、各向异性编码超材料对太赫兹波的极化调控和波束调控等。数值仿真和实验测试结果吻合很好,验证了编码超材料的出色性能,展示了编码超材料调控电磁波的多功能性。编码超材料对微波及太赫兹波的实时控制可用于制作波束分离、波束偏折、极化转换等功能器件,也可在宽带范围内有效缩减目标RCS。     

Response signal in a femtosecond pump-probe experiment in a condensed medium with account of the memory induced by the relaxation medium

For a model molecular system with one vibrational degree of freedom and three electronic states coupled by pump and probe laser pulses in a condensed medium, the response signal in a femtosecond pump-probe experiment is calculated. The potential curves of all three states are described by the Morse potential. Calculations are performed using two qualitatively different approaches to describing the medium-induced relaxation: with memory of the relaxation process and without memory (Markovian approximation). The temporal evolution of the vibrational wave packet in the intermediate electronically excited state is described using a master equation for the density matrix of the molecular system, which is derived within the framework of the Nakajima-Zwanzig formalism. It is demonstrated that, at short delay times, when the proposed approach is applicable, taking into account memory effects can substantially change the form of the pump-probe experiment signal in comparison with the signal calculated in the Markovian approximation.     

Theory,experiment and applications of metamaterials

In this review article, a brief introduction on the theory, experiments and applications of metamaterials is presented. The main focuses are concentrated on the composing meta-atoms, the method of transformation optics, the experimental demonstration of negative refraction, and the realizations of invisibility cloaks and electromagnetic black hole. At the end of this review, some typical applications of metamaterials, including high-performance antennas made of zero-refractive-index materials, inhomogeneous metamaterial lenses, and planar metasurfaces, are introduced in details.     

Dissipation-driven quantum phase transitions in a Tomonaga-Luttinger liquid electrostatically coupled to a metallic gate

The dissipation induced by a metallic gate on the low-energy properties of interacting 1D electron liquids is studied. As a function of the distance to the gate, or the electron density in the wire, the system can undergo a quantum phase transition from a Tomonaga-Luttinger liquid to two kinds of dissipative phases, one of them with a finite spatial correlation length. We also define a dual model, which describes an attractive one-dimensional metal with a Josephson coupling to a dirty metallic lead.     

Excitation spectra of coupled metallic slabs

The polarisability of the system consisting of two parallel thin metallic slabs within the jellium model is obtained within the assumption that the electron densities of the slabs do not overlap. It is then used to calculate, for the first time, the excitation spectra and dispersion relations of the collective surface excitations of that system. The dispersion relations are compared with the classical ones to enable the classification of the excitation modes.     

Characterization for metamaterials with a high refractive index formed by periodic stratified metallic wires array

Ultralong ZnO nanowires were successfully prepared on a large scale by a microwave-assisted aqueous route without using any surfactant or template at relatively low temperature of 120°C. The obtained nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectrum (EDX). The growth mechanism and photoluminescence of the one-dimensional nanostructure, and photovoltaic performances for dye-sensitized solar cell (DSSC) of the nanowires were discussed in detail.     

Retrieval of effective parameters for bianisotropic metamaterials with omega shaped metallic inclusions

Bianisotropic metamaterials including Ω-shaped metallic elements are investigated experimentally and theoretically. A passband is observed for a composite metamaterial (CMM) based on an Ω-medium below the plasmonic frequency of the corresponding closed CMM. The effective parameters (refractive index, impedances, permittivity, permeability, and magnetoelectric coupling coefficient) are retrieved for the Ω-medium and the CMM based on it. Our retrieval results show that the passband observed for the CMM is a band with positive refractive indices. Our retrieval results confirm the deductions of our previous reports.     

Theory of light amplification in active fishnet metamaterials

We establish a theory that traces light amplification in an active double-fishnet metamaterial back to its microscopic origins. Based on ab initio calculations of the light and plasmon fields we extract energy rates and conversion efficiencies associated with gain and loss channels directly from Poynting's theorem. We find that for the negative refractive index mode both radiative loss and gain outweigh resistive loss by more than a factor of 2, opening a broad window of steady-state amplification (free of instabilities) accessible even when a gain reduction close to the metal is taken into account.     

Superradiant optical emitters coupled to an array of nanosize metallic antennas

We study the properties of an array of Au ring nanoantennas fed by an ensemble of coherent emitters. The luminescence of the emitters is strongly enhanced at certain wavelengths due to the excitation of two types of resonances-the diffractive Rayleigh anomalies associated with the opening of new diffraction orders and the localized surface plasmons of the nanoantennas. We show that the two families of resonances can spectrally overlap and lead to anticrossings or cumulative enhancements depending on the symmetries of the modes. This rich optical behavior induces marked changes in the linewidth, shape, and amplitude of the peaks and could be potentially used to tune the luminescence of superradiant sources with new flexibility.     

Lamellar model of the left-handed metamaterials composed of metallic split-ring resonators and wires

Left-handed materials composed of split ring resonators (SRRs) and wires are investigated in the viewpoint of lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials staked alternatively. Several configurations of the SRR-wire metamaterial are numerically simulated to confirm its left-handed response as an analogy to the ENG-MNG lamellar model.     

Experimental and numerical study of omega type bianisotropic metamaterials combined with a negative permittivity medium

We report on the transmission properties of the omega (Ω) type metamaterials. Transmission through the periodic Ω-only and Ω-wire metamaterials are studied experimentally and numerically. A resonance band gap is observed for the periodic Ω medium around the resonance frequency of the single Ω unit cell. A transmission band is observed below the resonance band gap, when the periodic Ω structure is embedded in a negative permittivity medium composed of thin metallic wire arrays. We also studied the effect of periodicity on the transmission spectra of Ω type metamaterials.     

Solitons in a medium with linear dissipation and localized gain

We present a variety of dissipative solitons and breathing modes in a medium with localized gain and homogeneous linear dissipation. The system possesses a number of unusual properties, like exponentially localized modes in both focusing and defocusing media, existence of modes in focusing media at negative propagation constant values, simultaneous existence of stable symmetric and antisymmetric localized modes when the gain landscape possesses two local maxima, as well as the existence of stable breathing solutions.