液晶染料填充阶梯型Double-period结构局域模的光学特性

利用传输矩阵法研究了液晶染料填充一维阶梯型Double-period第四代准周期结构局域模的光学特性。计算了增益前局域模与外加电场方向和正入射波方向间夹角θ的变化关系,分析了增益系数与局域模透射率的关系以及局域模在空间位置的光场分布,讨论了增益后的局域模透射率与光场强度的关系。结果表明:随着夹角θ的增大,光子禁带变宽并且只向短波方向拓展;随着夹角θ的增大,增益前的局域模向短波方向移动,透射率逐渐增大,且局域模波长的调控量为23.7nm。随着增益系数的增大,透射率先增大后减小。光场分布呈现局域现象,当夹角θ=43.4°,波长λ=595.0nm时,光强达到6个数量级。增益后的局域模透射率与光场强度呈正比关系。     

Optical properties of a system of two coupled vertical microcavities

The interaction of two localized optical states in a structure consisting of a system of two coupled vertical microcavities is studied. It is shown that the interaction of two localized optical modes in coupled microcavities cause the modes to split. The optical properties of a system of coupled microcavities and the dispersion relations for the characteristic optical modes of the system are analyzed. Zh. Tekh. Fiz. 68, 94–97 (May 1998)     

Optomechanical coupling in a two-dimensional photonic crystal defect cavity

Periodically structured materials can sustain both optical and mechanical modes. Here we investigate and observe experimentally the optomechanical properties of a conventional two-dimensional suspended photonic crystal defect cavity with a mode volume of ~3(λ/n)3. Two families of mechanical modes are observed: flexural modes, associated to the motion of the whole suspended membrane, and localized modes with frequencies in the GHz regime corresponding to localized phonons in the optical defect cavity of diffraction-limited size. We demonstrate direct measurements of the optomechanical vacuum coupling rate using a frequency calibration technique. The highest measured values exceed 80 kHz, demonstrating high coupling of optical and mechanical modes in such structures.     

二维随机增益介质中局域模的模面积和放大

随机激光形成于随机介质中局域模的放大,其放大特性依赖于局域模的空间分布。通过复折射率的虚部将光学增益引入系统,采用时域有限差分(FDTD)法,分析了增益介质中局域模的放大特性,并用模面积描述了局域模空间分布,着重对比分析了模面积对局域模放大特性的影响。模拟结果显示,局域模具有不同的空间分布,直接影响了局域模的放大特性,模面积较小的模式具有较低的损耗,能够获得更多能量,在介质中被优先放大,而模面积较大的模式,由于损耗较大,将获得较少的能量。     

Beam propagation in gain–loss balanced waveguides

Linear and nonlinear localized modes of a slab waveguide with distributed gain and loss are studied. The structure is an optical analog of parity-time symmetric potentials in quantum mechanics. Such waveguide structures support stable localized modes. The explicit equation for the propagation constant of linear modes is obtained. The existence of stable nonlinear modes in such waveguides is demonstrated. Bend losses in such structures are analyzed.     

Two-dimensional photonic crystals with a lattice defect: Spectrum of defect modes, localization of light, and formation of evanescent waves

Properties of an electromagnetic field localized in the defect modes of two-dimensional photonic crystals are studied. The defect-mode spectrum of these structures is calculated, electromagnetic field localization and channeling effects are analyzed, and the properties of the field inside and beyond a photonic crystal with a lattice defect are also studied. The calculations show that the electromagnetic field is localized in the defect mode of a photonic crystal in a region smaller than the wavelength. The dependence of the defect-mode spectrum on the parameters of the photonic crystal is investigated and possibilities for controlling the spectrum of defect modes are indicated. It is shown that the optical field leaving a photonic crystal possesses the properties of a evanescent wave, which means that spatial resolution substantially greater than the wavelength of the radiation can be achieved in the near field and opens up possibilities for using photonic crystals with a lattice defect in near-field optical microscopy. The possibility of externally controlling an optical field localized in the defect modes of a photonic crystals is demonstrated.     

Solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain

By use of the Hartree approximation and the method of multiple scales, we investigate quantum solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain. It is shown that there exist solitons of two different quantum frequency bands: i.e., magnetic optical solitons and acoustic solitons. At the boundary of the Brillouin zone, these solitons become quantum intrinsic localized modes: their quantum eigenfrequencies are below the bottom of the harmonic optical frequency band and above the top of the harmonic acoustic frequency band.     

钉扎效应对聚噻吩中双空穴极化子附近局域振动模的影响

基于扩展的二维Su-Schrieffer-Heeger模型，研究了库仑钉扎作用对聚噻吩中双空穴极化子 附近的局域振动模的影响.除了与激发方式无关的本征振动模外，发现了与激发方式相关的 声子振动模式.计算结果与聚噻吩红外和拉曼光谱实验数据相当符合，从而对掺杂诱导和光 致激发下聚噻吩吸收光谱的区别给出了较好的理论阐释. 关键词： 聚噻吩 钉扎效应 吸收光谱 局域振动模     

Dynamics of a finite harmonic oscillator chain with a surface impurity

A method is presented for constructing the normal modes and spectrum of a finite harmonic oscillator chain to which a polyatomic surface impurity is attached. This scheme is a generalization of an earlier theory due to Puszkarski. Special attention is devoted to localized surface modes and to the identification of the circumstances which cause them to occur. Diagnostic calculations have been performed in order to learn how an adsorbed diatomic molecule alters the normal modes and eigenfrequencies of the lattice. Examples are provided of cases where these effects are slight and of others where the perturbation generates localized optical and/or acoustic surface modes.     

Nano-infrared imaging of localized plasmons in graphene nano-resonators

We conduct in-situ near-field imaging of propagating and localized plasmons(cavity and dipole modes) in graphene nano-resonator. Compared with propagating graphene plasmons, the localized modes show twofold near-field amplitude and high volume confining ability(~ 10~6). The cavity resonance and dipole mode of graphene plasmons can be effectively controlled through optical method. Furthermore, our numerical simulation shows quantitative agreement with experimental measurements. The results provide insights into the nature of localized graphene plasmons and demonstrate a new way to study the localization of polaritons in Van der Waals materials.     

随机激光器中准态腔的阈值与其局域化程度的关系

基于光波在有限随机介质中的局域化理论，利用有限时域差分法数值求解Maxwell方程 组，研究了随机介质中的激光现象，分析了准态模的放大与其 空间局域性的关系. 通过研究二维非增益随机介质中光波的局域化，确定了准态模的空间分 布和频谱特征. 通过引入增益，研究了准态模的放大过程和阈值特性. 结果表明空间局域化 强的准态模在增益介质中被优先放大，且有较低的阈值. 关键词： 随机激光器 准态模 随机介质中的光学特性     

Nonlinear localized modes at phase-slip defects in waveguide arrays

We study light localization at a phase-slip defect created by two semi-infinite mismatched identical arrays of coupled optical waveguides. We demonstrate that the nonlinear defect modes possess the specific properties of both nonlinear surface modes and discrete solitons. We analyze the stability of the localized modes and their generation in both linear and nonlinear regimes.     

Field patterns in periodically modulated optical parametric amplifiers and oscillators

Spatially localized and periodic field patterns in periodically modulated optical parametric amplifiers and oscillators are studied. In the degenerate case (equal signal and idler beams) we elaborate on the systematic method of construction of the stationary localized modes in the amplifiers, and study their properties and stability. We describe a method of constructing periodic solutions in optical parametric oscillators, by adjusting the form of the external driven field to the given form of either signal or pump beams.     

Localized optical subcycle pulses in dispersive media

The conditions for creation of broadband localized optical fields (Bessel X pulses and focus wave modes) in dispersive media are analyzed. It is shown that transmission of focus wave modes with subcycle pulse durations through fused silica is possible.     

Generation of multi-axis Laguerre–Gaussian beams from?geometric modes of a hemiconfocal cavity

We study the transformation of multi-axis Laguerre–Gaussian beams from optical beams comprising Hermite–Gaussian modes with ray–wave duality. By use of cylindrical lenses, Hermite–Gaussian modes can be transformed into Laguerre–Gaussian modes possessing optical orbital angular momentum. The superposed Hermite–Gaussian modes localized on geometric trajectories are generated from a degenerate hemiconfocal cavity and transformed into multi-axis Laguerre–Gaussian beams. Experimental results of the structured beams are systematically manipulated and in good agreement with theoretical analyses.     

Near-field observation of subwavelength confinement of photoluminescence by a photonic crystal microcavity

We present a direct, room-temperature near-field optical study of light confinement by a subwavelength defect microcavity in a photonic crystal slab containing quantum-well sources. The observations are compared with three-dimensional finite-difference time-domain calculations, and excellent agreement is found. Moreover, we use a subwavelength cavity to study the influence of a near-field probe on the imaging of localized optical modes.     

Optical scar in a chaotic fiber

We propose to use a multimode optical fiber with a D-shaped cross section as a privileged system to image wavefunctions of a chaotic system. Scar modes are in particular the subject of our investigations. We study their imprints on the statistics of intensity and we show how the introduction of a localized gain region in the fiber is used to perform a selective amplification of scar modes.     

金属卤化物中的晶格振动

运用紧束缚双带模型对MX化合物晶格振动的计算发现,晶格振动谱由一条声频支和三条光频支组成,进一步得到了出现元激发时,晶格振动色散关系中的分立频率和相应的定域振动模.在MX化合物红外吸收谱的计算中发现对应不同元激发红外谱具有不同的特征. 关键词： 电荷密度波 晶格振动 红外吸收     

Two-color nonlinear localized photonic modes

We analyze second-harmonic generation (SHG) at a thin effectively quadratic nonlinear interface between two linear optical media. We predict multistability of SHG for both plane and localized waves, and also describe two-color localized photonic modes composed of a fundamental wave and its second harmonic coupled together by parametric interaction at the interface.     

Discrete solitons and nonlinear surface modes in semi-infinite waveguide arrays

We discuss the formation of self-trapped localized states near the edge of a semi-infinite array of nonlinear optical waveguides. We study a crossover from nonlinear surface states to discrete solitons by analyzing the families of odd and even modes centered at finite distances from the surface and reveal the physical mechanism of the nonlinearity-induced stabilization of surface modes.