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1.
2.
Specific features of the defect modes of cholesteric liquid crystals (CLCs) with an isotropic defect, as well as their photonic
density of states, Q factor, and emission, have been investigated. The effect of the thicknesses of the defect layer and the system as a whole,
the position of the defect layer, and the dielectric boundaries on the features of the defect modes have been analyzed. It
is shown that when the CLC layer is thin the density of states and emission intensity are maximum for the defect mode, whereas
when the CLC layer is thick, these peaks are observed at the edges of the photonic band gap. Similarly, when the gain is low,
the density of states and emission intensity are maximum for the defect mode, whereas at high gains these peaks are also observed
at the edges of the photonic band gap. The possibilities of low-threshold lasing and obtaining high-Q microcavities have been investigated. 相似文献
3.
Arkhipkin VG Gunyakov VA Myslivets SA Zyryanov VY Shabanov VF 《The European physical journal. E, Soft matter》2007,24(3):297-302
A one-dimensional ZrO2/SiO2 photonic crystal with a 4-n -pentyl-4' -cyanobiphenyl (5CB) nematic defect layer was used to investigate the transmission spectra of light polarized
parallel and perpendicular to the liquid-crystal director at different angles of incidence. The spectra of the photonic crystal
were shown to split into four polarized components Tij at oblique incidence. When the incident angle increased, the bandgap edges and the defect modes shifted towards short wavelengths,
while the amplitudes of the defect modes increased for the transverse magnetic polarization and decreased for the transverse
electric polarization. The observed discrepancy between the defect mode amplitudes in the center and near the edges of the
photonic bandgap was found to be related to the radiation losses inside the defect layer of a non-ideal photonic crystal.
The simulated transmission spectra obtained using recurrence relations and taking into account the decay of defect modes are
in good agreement with the experimental data. 相似文献
4.
In this work, we theoretically investigate the properties of defect modes in a defective photonic crystal containing a semiconductor metamaterial defect. We consider the structure, (LH)N/DP/(LH)N, where N and P are respectively the stack numbers, L is SiO2, H is InP, and defect layer D is a semiconductor metamaterial composed of Al-doped ZnO (AZO) and ZnO. It is found that, within the photonic band gap, the number of defect modes (transmission peaks) will decrease as the defect thickness increases, in sharp contrast to the case of using usual dielectric defect. The peak height and position can be changed by the variation in the thickness of defect layer. In the angle-dependent defect mode, its position is shown to be blue-shifted as the angle of incidence increases for both TE and TM waves. The analysis of defect mode provides useful information for the design of tunable transmission filter in semiconductor optoelectronics. 相似文献
5.
Transmission characteristics of nonlinear one dimensional photonic crystal with a defect have been studied. GaAs/Si multilayer structure with a single defect has been simulated using transfer matrix method. In this study refractive indices of both layers have been taken to be dependent on intensity and wavelength simultaneously. It is found that central wavelength of defect mode change with intensity of wave. Average change in central wavelength of defect mode is 0.02 nm/(1 GW/cm2). This property can be exploited in the design of a single channel tunable wavelength division demultiplexer for optical communication. 相似文献
6.
H. W. Yang D. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(2-3):387-392
This paper presents a parallel frequency-dependent finite-difference time-domain ((FD)2TD) method for plasma in the dispersive media. Results obtained with parallel and serial algorithms verify that parallel (FD)2TD has the same precision as the serial (FD)2TD, while the parallel approach could reduce the CPU time efficiently. A tunable filter is analyzed based on a one-dimensional photonic crystal containing a plasma defect by this method. The tunability of the photonic crystal filter can be achieved by adjusting the defect layer parameters instead of changing the dimension of photonic crystal. 相似文献
7.
设计了一种新型矩形点阵光子晶体光纤,该光纤纤芯缺失一根空气柱,包层沿光纤长度方向在普通矩形点阵光子晶体光纤中每两列之间隔一行插入一列空气孔而形成正方形网孔结构.采用全矢量有限元法并结合各向异性完美匹配边界条件,对该光纤的色散、双折射和约束损耗进行了数值模拟.结果发现,该光纤具有高双折射负色散效应和较强的模约束能力,约束损耗小于10-2dB·m-1,通过改变光纤结构参数(即空气孔间隔Λ和相对孔间隔d/Λ),可以调节该光纤高双折射负色散工作波长.若调整光纤结构参数Λ=2.0μm,d/Λ=0.4,该光纤在C波段(1.53—1.565μm)呈现负色散并具有负色散斜率,双折射高达10-2,非线性系数接近55km-1W-1.该光纤将在保偏光通信、色散补偿以及基于四波混频的波长转换器设计等方面具有重要的应用. 相似文献
8.
《Physics letters. A》2019,383(21):2551-2560
Optical characteristics of two new graphene based photonic crystals are studied in detail. A structure containing alternating layers of graphene and SiO2 slabs is considered as the ideal crystal. The dependency of the photonic band gaps (PBGs) to the dielectric layer thickness and the period number is explored at first step. Potential of the proposed crystal to be used as an optical filter is then investigated. Adding a nonlinear electro-optic polymer as a defect layer, the alterations of the optical features are inspected. Results show that the defect layer insertion causes a resonant mode inside the PBGs. However, the location of the defect layer inside the crystal is very effective on both the frequency and width of the resonant mode. Tunability of the optical features is probed by taking into account of the dependencies to the wave incident angle, graphene chemical potential and the applied external voltage to the defect layer. 相似文献
9.
S. Ya. Vetrov A. Yu. Avdeeva R. G. Bikbaev I. V. Timofeev 《Optics and Spectroscopy》2012,113(5):517-521
Spectral properties of a 1D photonic crystal that is comprised of two multilayered dielectric mirrors and a nanocomposite layer between them as a structural defect are studied. The nanocomposite consists of silver nanoballs dispersed in a transparent matrix and is characterized by an effective resonant permittivity. The spectral manifestation of the defect mode splitting for the s-polarized waves is studied as a function of the angle of incidence and concentration of nanoballs. Specific features of the transmission spectra for the s- and p-polarized waves are established for the angle of incidence equal to the Brewster angle of the seeding photonic crystal. It is shown, in particular, that, in the region of the continuous transmission spectrum of the spolarized waves, there arises an additional bandgap caused by mixing of the resonant mode with photonic modes. 相似文献
10.
<正>A novel polarization channel drop filter(PCDF) based on two-dimensional(2D) photonic crystals(PCs) is presented.It consists of two line defect waveguides and two point defect micro-cavities.In the line-defect waveguides,the transverse-electric(TE) and transverse-magnetic(TM) polarization lights are guided using photonic band-gap and total internal reflection effect,respectively.The light at the resonant frequency for TE polarization can be transferred from one waveguide to the other using the proposed system.Compared with the existing four-port PCDF based on PCs,the three-port structure can realize a multi-channel wavelength system of PCDF more easily and can be an essential device in future polarization wavelength division multiplexing(PWDM) systems. 相似文献
11.
Band gaps and nonlinear defect modes in one-dimensional photonic crystals with anisotropic single-negative metamaterials 总被引:1,自引:0,他引:1
Tingting Tang Wenli Liu Xiuying Gao Xiujun He Jun Yang 《Optics & Laser Technology》2011,43(6):1016-1019
We propose a one-dimensional photonic crystal (1DPC) with multilayered periodic structures containing dispersive anisotropic single-negative (ASNG) (permittivity- or permeability-negative) metamaterials. The influences of the ratio of dA/dB and their scale on ASNG gaps are discussed. Moreover, the effect of a nonlinear defect layer introduced into the proposed structure is also analyzed, and the results show that the defect mode has two peaks of electrical fields in the defect layer and its bistability property is also different from a defect mode in PCs with isotropic SNG gaps. 相似文献
12.
Anomalous infrared monochromatic transmission through superconducting cylinders embedded in a dielectric and dielectric cylinders
embedded in a superconductor is found. The transmitted frequency corresponds to the localized photonic mode in the forbidden
photonic band. This localized mode appears when the symmetry of the photonic crystal is broken by a defect. This defect can
be formed when supercon-ducting cylinder is removed from the node of the ideal two-dimensional lattice of superconducting
cylinders in dielectric medium or one dielectric cylinder placed out of the node of the lattice of the dielectric cylinders
in superconducting medium. The corresponding frequency was calculated for the YBa2Cu3O7 − δ
supercon-ducting cylinders in vacuum. 相似文献
13.
提出了一种变态光子带隙结构,研究了由这种结构构成的周期慢波系统的Cherenkov辐射源的特性. 利用高频仿真软件以及三维粒子模拟软件对变态及常态光子带隙慢波系统中类TM01模的色散特性及注-波互作用物理过程进行了模拟研究. 结果表明,在变态光子带隙慢波系统中,类TM01模纵向场分量沿角向分布均匀性得到明显改善,能有效抑制非对称模式,提高输出频谱纯度及注-波互作用效率.
关键词:
Cherenkov辐射源
变态光子带隙结构
慢波系统
三维粒子模拟 相似文献
14.
M. Sahrai S. Aas M. Aas M. Mahmoudi 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):337-342
The Hartman effect in one-dimensional photonic crystals contained a defect layer doped
with two-level, and three-level atoms is discussed. It is shown that the transmitted phase
time in one-dimensional photonic crystals contained a defect layer reaches to a positive
constant as the periodic number N increases. However, for a defect layer
doped by two-level atoms, the transmitted phase time reaches to negative constant by
increasing periodic number N. In addition, for defect layer doped by
three-level atoms, the transmitted phase time can be controlled from positive to negative
just by the Rabi-frequency of coupling field. 相似文献
15.
光子晶体光纤的弯曲损耗振荡特性分析 总被引:2,自引:1,他引:1
综合运用弯曲光纤的等效直光纤模型、全矢量频域有限差分法及各向异性完全匹配层吸收边界,计算了两种类型(折射率引导型和带隙型)光子晶体光纤(PCF)的弯曲损耗.通过数值模拟弯曲损耗随弯曲半径的变化关系,证实了两种光子晶体光纤均具有弯曲损耗振荡特性.进而分析了两种光子晶体光纤弯曲损耗振荡的产生机理并给出了与损耗峰对应的包层模式.结果表明,振荡的产生源于基模与包层模式的耦合,其中,折射率引导型光子晶体光纤的弯曲损耗振荡机理类似于传统双包层光纤,带隙型光子晶体光纤弯曲损耗振荡的产生则是两种不同类型的包层模式共同作用的结果. 相似文献
16.
《Waves in Random and Complex Media》2013,23(3):359-366
Abstract A study of defect-mode propagation in lossless layered photonic media has been performed. We put forward a new proper characteristic of the defect cavity, called the coupling length of the defect, namely, a maximum spatial radius around the defect site, within which the defect mode couples into the tunnelled incident wave. This coupling length allows us to optimize the values of the Q-factor and the transmission coefficient with respect to both the position of the defect and the dielectric permittivity of the defective layer. 相似文献
17.
In the present paper, a novel photonic crystal (PC) defect mode is designed by inserting a ferroelectric material layer (LiNbO3) into Si/C60 one-dimensional PCs. The band structure of the ferroelectric PCs is numerically analyzed by the transfer matrix method (TMM). The width of the photonic band gap increases by 80 nm and a defect mode appears at a central wavelength of 680 nm when a 150 nm LiNbO3 layer is inserted into the Si/C60 PC structure. The defect mode in the band gap shifts linearly with the change in electric field. The defect mode shifts by 11.2 nm toward shorter wavelengths when the thin film is subjected to a DC voltage of 1 KV. 相似文献
18.
The photoluminescence (PL) spectra of n- and p-type Al
x
Ga1−x
As (x>0.42) grown by metalorganic vapor phase epitaxy (MOVPE) and liquid phase epitaxy show typically a broad PL band (BB) centered
about 300meV below the near band-gap PL lines. In the MOVPE grown samples the BB is composed out of four lines. The BB intensity
increases with the doping level and dominates the spectrum at concentrations > 1017 cm−3. The temperature dependence of the BB intensity shows two distinct maxima at ≈ 19K and ≈ 80K. Hydrogenation of MOVPE grown
samples at 170°C reveal an effective passivation of the shallow acceptors and the centers associated with the BB line. On
the contrary hydrogenation at temperatures >250°C leads to an increase in the BB intensity which is related with the evaporation
of As from the surface and the generation of VAs in the layers at these temperatures. Our results suggest that the BB is related with isoelectronic centers formed when VAs and CAs or SiAs associate to form next nearest neighbor ion pairs. The PL is then due to a recombination of excitons in analogy to the case
of (Zn, O) isoelectronic complexes in GaP.
Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17,
1998.
This work was supported by the DFG under the contract AZ 436 TSE 113/22/0 in the framework of the cooperation between the
DFG and the Academy of Sciences of the Czech Republic. 相似文献
19.
利用微腔之间的立体耦合,提出了基于无源材料硅的双层光子晶体薄板H1(DLPCS-H1)腔,薄板之间为空气层.使用三维时域有限差分方法和Padé近似方法分析了DLPCS-H1腔的偶极模的场分布和品质因子.通过对中间空气层高度的优化使DLPCS-H1腔的偶极模的品质因子得到了显著的提高,大约为单层光子晶体薄板H1腔的偶极模的品质因子的4倍.此外,还研究了三层光子晶体薄板H1腔,它的偶极模的品质因子约为单层光子晶体薄板H1腔的偶极模的品质因子的7倍. 相似文献
20.
用一维光子带隙结构增强硫化镉双光子吸收研究 总被引:2,自引:2,他引:0
用真空镀膜方法制备了含有单个CdS缺陷层的具有不同周期和结构参量的TiO2/SiO2一维光子晶体。用抽运一探测技术研究了CdS缺陷层的双光子吸收(TPA)现象。实验结果表明:一维光子晶体中CdS缺陷层的双光子吸收显著增强。不同周期和结构参量的一维光子晶体中CdS缺陷层的双光子吸收系数不同。双光子吸收的增强来源于由光局域化导致的缺陷层的电场强度的增加。缺陷层电场强度与一维光子晶体的结构有关,如周期,光子带隙的位置与宽度及缺陷模式等因素都会影响缺陷层电场强度。采用四分之一波长的高低折射率介质层和与入射波长匹配的缺陷模可以得到最大的缺陷层电场强度。 相似文献