Tuning of the photonic band gaps and the reflection spectra of a one-dimensional photonic crystal based on silicon and a liquid crystal

The reflection spectra and the photonic band gaps of a one-dimensional composite photonic crystal are calculated for different filling factors (the ratio of the thickness of a silicon layer to the lattice constant A). A change in the refractive index of the filler in a photonic crystal leads to the shift of both edges for certain side photonic bands. It is shown that, with a change in the refractive index from 1.49 to 1.69, the shift of the edges (the tuning effect) can reach the value A/λ = 0.04 for the main photonic band and 0.08 for a side band. An additional criterion for designing a photonic crystal is the estimation of the sharpness of the edges of photonic bands in the reflection spectra.     

Optical Tamm states at the interface between a photonic crystal and a nanocomposite with resonance dispersion

Optical Tamm states localized at the edges of a photonic crystal bounded from one or both sides by a nanocomposite have been studied. The nanocomposite consists of metallic nanoinclusions, which have a spherical or orientationally ordered spheroidal shape and are dispersed in a transparent matrix, and is characterized by the resonant effective permittivity. The transmission, reflection, and absorption spectra have been calculated for waves with longitudinal and transverse polarizations in such structures at the normal incidence of light. The spectral manifestation of Tamm states that is due to the existence of negative values of the real part of the effective permittivity has been analyzed for the visible spectral range. It has been established that the characteristics of Tamm states localized at the edge of the photonic crystal depend strongly both on the concentration of nanoballs in the nanocomposite film and on its thickness. Modes formed by two coupled Tamm plasmon polaritons localized at the edges of the photonic crystal adjacent to two nanocomposite layers have been examined. It has been shown that, in the case of the anisotropic nanocomposite layer adjacent to the photonic crystal, each of two orthogonal polarizations of the incident wave corresponds to a specific frequency of the Tamm state localized at the edge; owing to this property, the transmission spectra of such a structure are polarization sensitive.     

Control of absorption spectrum of a one-dimensional resonant photonic crystal

The crystal under consideration is a layered structure consisting of alternating layers of two materials, one of which is a resonantly absorbing gas. It is shown that the combination of the dispersion of an atomic gas with the dispersion of a photonic-bandgap structures allows one to efficiently control the transmission spectra of s- and p-polarized modes in these combined systems. It is found that the spectrum is highly sensitive to the position of the gas resonance frequency with respect to the bandgap edge and to a change in the gas pressure. The transmission, reflection, and absorption spectra of the resonant photonic crystal are studied at an angle of incidence equal to the Brewster angle of a seed photonic crystal. Possible applications of the found particular features of the dispersion of resonant photonic crystals are discussed.     

Spectral properties of a one-dimensional resonant photonic crystal

The eigenexcitation and transmission spectra of a one-dimensional resonant photonic crystal are studied for TM and TE polarized electromagnetic waves. The crystal considered is a layered structure consisting of alternating isotropic layers and layers of a resonantly absorbing gas. The performed calculations show that the band structure of the spectra of the resonant photonic crystal significantly changes as the angle of incidence and the density of the resonant gas are varied. The structure of the spectra of additional transmission in the bandgap of the resonant photonic crystal is studied taking into account the decay of electromagnetic modes. The possibilities of controlling the spectrum of electromagnetic modes are indicated.

     

Diffraction mechanism of specular reflection of light from photonic crystals

The spectra of specular reflection and diffraction of light for a resonant two-dimensional photonic crystal consisting of semiconductor cylinders embedded in a dielectric matrix, as well as the exciton-polariton band structure of this crystal, are studied theoretically. It is shown that specular reflection of light from a photonic crystal can be considerably enhanced by diffraction in the photonic crystal and reflection from its inner boundary with vacuum.     

Thermo‐tunable defect mode in one dimensional photonic structure based on grooved silicon and liquid crystal

A composite 1D photonic structure with defect was designed, fabricated by wet anisotropic etching of (110)‐oriented silicon and filled with liquid crystal. The polarized reflection spectra of the second‐order stop band with defect mode have been registered by means of FTIR microscopy. The thermo‐optical effect in the photonic structure due to phase transition in liquid crystal has been demonstrated in the spectral region of 8.5 µm. The relative shift of the defect mode peak was found experimentally to be 2.0% compared to 3.1% as predicted by calculation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Coherent transmission and reflection spectra of ordered structures from spherical alumina particles

In this paper, two novel types of semi-slow light photonic crystal waveguide with large transmission bandwidth obtained by shifting the boundaries of a W1 waveguide in the direction of light propagation are presented. One includes air rings localized at only one side of the line defect and the other replaces the holes at each side of the waveguide by the uniform air rings which are constructed by the homocentric square dielectric rod inserted into the air holes. The structure produces unusual “n-type” transmission spectrum depending on the different parameters such as inner radius of air ring, dielectric constant of square dielectric rod, etc. It is shown that the transmission spectra of the two structures are completely different from each other. A versatile control of light propagation with large normalized bandwidth and slow light phenomena can be obtained using a unique geometrical parameter. Numerical simulation by the finite-difference time-domain (FDTD) method demonstrates the propagation of the broadband pulse.     

可见光波段SiO2/CdSe一维光子晶体及缺陷模的研究究

采用SiO2/CdSe构建了可见光波段一维光子晶体结构,并在其中引入LiTaO3缺陷层。利用传输矩阵法,分析了电磁波在无缺陷与含LiTaO3缺陷层两种光子晶体中的带隙结构,系统地研究了缺陷层参数对光子晶体可见光波段带隙结构的影响规律。计算结果表明：LiTaO3的引入,有利于带隙宽度的增加,调整缺陷层结构参数,缺陷模的位置可在不同颜色区域出现,如红光、黄光等缺陷模。该结构有望用于制作可见光波段的滤波器。     

Preparation of one-dimensional porous silicon photonic quantum-well structures

One-dimensional porous silicon (PSi) photonic quantum-well structures have been electrochemically fabricated and spectroscopically characterized. The photonic well in the structure is a photonic crystal (PC) consisting of alternately stacked high- and low-refractive-index PSi layers. Discrete states are observed in both reflectance and transmission spectra. It is found that the number of confined states appearing in the photonic bandgap of the photonic barrier depends on the number of periods adopted in the well PC. Thus, increased confined photonic states can be created simply by increasing the number of periods of the well PC in the structures. Received: 26 February 2002 / Accepted: 17 May 2002 / Published online: 4 December 2002 RID="*" ID="*"Corresponding author. Fax: +86-21/6510-4949, E-mail: xyhou@fudan.edu.cn     

DOUBLE PERIODIC PHOTONIC CRYSTAL WITH METAMATERIAL

In this paper, the reflection and transmission coefficients of multi-layer dielectric and metamaterial media are derived by transmission-line method. Then, it is applied to double periodic photonic crystal structure, which is composed of two thin dielectric layers sandwiched by two thin metamaterial layers. The results show the structure has a large passband and a monotonous symmetric rising band edges compared with that for a conventional photonic crystal structure. If a defect layer is introduced, the localized modes appear. Furthermore, the number of transmission peaks in the photonic crystal structure can be tuned by changing the thickness of the defect in the structure. This photonic crystal may find application to broadband reflectors and the multi-wavelength narrow band optical filters.     

Specific features of polarization anisotropy in optical reflection and transmission of colloidal photonic crystals

This paper reports on the measurements (in linearly polarized light) of the transmission and reflection spectra of colloidal photonic crystals with three-dimensional and one-two-dimensional photonic band structure, i.e., opal films and Langmuir-Blodgett crystals with a refractive index contrast of ∼1.5: 1.0. It has been shown that the polarization anisotropy is enhanced considerably in the diffraction resonance range both in transmitted and reflected light, and that the anisotropy in the resonance range can be as high as 99%. The interaction of photonic crystal eigenmodes has been found to affect the polarization anisotropy. The assumption has been made that the coincidence of the maxima in polarization anisotropy of the resonant and nonresonant light reflection in colloidal crystals originates from the disorder in their lattices. The generality of the results obtained is confirmed by the fact that the polarization anisotropy manifests itself in the same way in colloidal crystals with different lattice symmetries.     

Nonlinearities in the reflection and transmission spectra of the photonic bandgap heterostructures with n–i–p–i crystals

Nonlinear optical properties of photonic crystal heterostructures with embedded n–i–p–i superlattices are investigated. Self-consistent calculations of the transmission and reflection spectra near the defect mode are performed using the transfer-matrix method and taking into account the gain saturation. Analysis of features and output characteristics is carried out for one-dimensional photonic crystal heterostructure amplifiers in the GaAs–GaInP system having at the central part an active “defect” from doubled GaAs n–i–p–i crystal layers. The gain saturation in the active layers in the vicinity of the defect changes the index contrast of the photonic structure and makes worse the emission at the defect mode. Spectral bistability effect, which can be exhibited in photonic crystal heterostructure amplifiers, is predicted and the hysteresis loop and other attending phenomena are described. The bistability behavior and modulation response efficiency demonstrate the potential possibilities of the photonic crystal heterostructures with n–i–p–i layers as high-speed optical amplifiers and switches.      

Anisotropy of nonlinear optical transmission at the edge of the photonic band gap of an apodized layered medium

The effect of Kerr nonlinearity on the transmission of laser radiation in a one-dimensional photonic crystal has been investigated by the transfer-matrix method, modified to describe nonlinear effects. The crystal under study is a thin-film multilayer structure with a spatial distribution of the refractive index, which makes it possible to eliminate side bands in the transmission spectrum at each side of the photonic band gap and significantly increase the slope of the transmission curve. The transmission spectrum of such a photonic crystal structure has been studied for two opposite directions of laser radiation propagation. The anisotropy of nonlinear transmission is most pronounced near the edge of the photonic crystal band gap, which lies in the near-IR region. The proposed structure, having strong transmission anisotropy and sufficiently low reflection in the forward direction, can operate as an optical diode (analog of an electron diode).     

Effect of dimensionality on the spectra of hybrid plasmonic-photonic crystals

Based on colloidal crystals of various dimensionality, hybrid metal-dielectric plasmonic-photonic heterocrystals have been prepared. It has been shown that the spectra of optical transmission of heterocrystals are mostly controlled by the sum of contributions of composing plasmonic and photonic crystals. At the same time, there are a number of phenomena caused by the mutual effect of heterostructure components, which lead to a deviation of observed optical properties from the linear superposition of responses of these crystals. In particular, it has been found that the anomalous transmission controlled by the plasmonic crystal decreases with increasing the dimensionality of the photonic crystal attached to it. At the same time, light reflection on a metallized surface changes light diffraction in photonic crystals and leads to Fabry-Perot oscillation amplification. It has been assumed that an intermediate layer is formed, in which Bloch modes of the photonic crystal and surface plasmon-polaritons of the plasmonic crystal are hybridized.     

光子晶体光纤非线性光谱特性的理论与实验研究

光子晶体光纤具有特殊的导光机制和结构可调性,可以产生奇异的色散特性及高非线性,为非线性光纤光学领域的研究提供了新的条件。受多种非线性光学效应的共同作用,在不同泵浦光脉冲参数条件下,不同结构参数及传输特性的光子晶体光纤能产生丰富的非线性光谱。利用分步傅里叶方法求解非线性薛定谔方程,模拟飞秒激光脉冲在光子晶体光纤中的传输过程,获得输出光谱与入射光脉冲参数(泵浦光峰值功率P、泵浦光波长λ、光脉冲形状、光脉冲宽度T_FWHM)、光纤结构参数(孔间距Λ、空气填充比d/Λ、光纤长度z)、传输特性(色散、非线性系数)的关系,分析拉曼孤子、色散波、自相位调制等非线性效应产生的光谱特性。利用光子晶体光纤包层节区进行非线性光学实验研究,获得了孤子波和色散波的宽带光谱输出。理论分析与实验测量的光谱中都包括了波长0.5 μm附近可见光波段的蓝移色散波、0.82 μm波段的剩余泵浦光、1.1 μm波段的孤子波、2 μm附近的红移宽带色散波。理论分析与实验测量结果一致,阐明光子晶体光纤中非线性光谱产生的物理原理,实现了对宽带光谱的可控输出,为高非线性光子晶体光纤的结构设计、制备及非线性光谱的应用研究奠定基础。     

Bistability of an optical response of a photonic crystal with a dense resonant medium as a defect

Optical characteristics of a system consisting of a photonic crystal with a defect layer of a dense resonant medium described by the modified Bloch equation are considered. Transmission spectra are calculated and regions of existence of bistable optical response of the system are found. It is shown that the effect of internal reflection demonstrated by the dense resonant medium results in variation of reflection and transmission spectra of the photonic crystal and the loop width of the bistable response of the dense resonant medium is determined by the structure of the photonic crystal. Original Russian Text ? D.V. Novitsky, S.Yu. Mikhnevich, 2008, published in Optika i Spektroskopiya, 2008, Vol. 104, No. 6, pp. 987–991.     

Energy‐lose induced unidirectional light propagation in porous alumina photonic crystal

Unidirectional light propagation phenomena are observed in the photonic crystal heterostructures based on anodic alumina membrane when the incident light illuminated from forward and backward directions. Transmittance / reflectance spectra measurements and theoretical calculations show that the origin of this kind of unbalanced reflection is ascribed to the energy loss induced by Rayleigh scattering. Importantly, unidirectional light propagation can be modulated over the whole visible light region by adjusting the combination of different photonic bandgap as well as the view angle. The as‐prepared heterostructures may provide potential applications in direction‐dependent photonic devices.     

Zone structure and polarization properties of the stack of a metamaterial-based cholesteric liquid crystal and isotropic medium layers

The optical properties of a stack of metamaterial-based cholesteric liquid crystal (CLC) layers and isotropic medium layers are investigated. The problem is solved by a modification of Ambartsumian’s layer addition method. CLCs with two types of chiral nihility are defined. The peculiarities of the reflection spectra of this system are investigated and it is shown that the reflection spectra of the stacks of CLC layers of these two types differ from each other. Besides, in contrast to the single CLC layer case, these systems have multiple photonic band gaps. There are two types of such gaps: those selective with respect to polarization of the incident light and nonselective ones. It is shown that the system eigenpolarizations mainly coincide with the quasi-orthogonal, quasi-circular polarizations for normally incident light, except the regions of diffraction reflection selective with respect to the polarization of incident light. The influence of the CLC sublayer thick-nesses, the incidence angle, the local dielectric (magnetic) anisotropy of the CLC layers, and the refractive indices and thicknesses of the isotropic media layers on the reflection spectra and other optical characteristics of the system is investigated.     

光子晶体光纤布拉格光栅传输谱特性的分析

研究光子晶体光纤中光纤光栅的传输谱特性对于研制基于光子晶体光纤的光纤光栅器件有着重要的意义。结合耦合模理论和光束传输相关函数方法,对一种典型光子晶体光纤中的布拉格光栅(FBG)传输谱进行了理论分析。比较了光子晶体光纤中布拉格光栅与常规布拉格光栅的传输谱。数值分析了光纤截面结构变化对于光栅传输谱的影响,并给出这种影响的定性解释。计算结果显示,与常规光纤光栅相比,包层模共振引起的损耗峰与正反向纤芯模耦合引起的损耗峰可以相比拟,而包层模共振的间隔也比常规光纤中光纤光栅的包层模共振间隔要大。同时给出了晶体光纤截面上空气孔的占空比,空气孔的排布层数对于传输谱影响的规律。