基于等离子体缺陷层的一维可调谐微波光子晶体滤波特性

等离子体填充到一维介质-真空微波光子晶体的缺陷层构成一种可调谐单通道滤波器.据等离子体的强色散特性,其等效折射率与电磁波频率及等离子体频率等参数有关,因而可以通过改变等离子参数,使一维微波光子晶体缺陷层的谐振频率发生偏移,实现微波光子晶体的可调谐滤波特性.介质层和等离子体层分别采用了时域有限差分（FDTD）算法及分段线性电流密度卷积时域有限差分（PLJERC-FDTD）算法.数值模拟表明,通过改变等离子体频率可以实现滤波通道在光子禁带内较大带宽范围的移动. 关键词： 等离子体 微波光子晶体 可调谐滤波     

Angular tuning of defect modes spectrum in the one-dimensional photonic crystal with liquid-crystal layer

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 T_ij 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.     

Investigation of defect modes in a defective photonic crystal with a semiconductor metamaterial defect

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/D^P/(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.     

多系双局域态光子晶体的可调谐滤波特性分析

利用紧束缚方法分析了双局域态光子晶体产生双缺陷模的机理, 采用传输矩阵法研究了一维光子晶体的光学传输特性, 并得到了透射谱与晶体结构参数的关系, 在此基础上讨论了光子晶体在受到单轴应力时所表现出的介观压光效应, 据此设计了一种结构简单的应力调制的近红外波段的多通道滤波结构.通过数值模拟可以看出, 随着各介质层折射率或厚度的增加, 缺陷模发生红移.当对多系双局域态光子晶体施加单轴拉伸应力时, 各缺陷峰都向长波长移动, 且缺陷峰峰值基本不变.经过数值拟合, 缺陷峰中心波长与对光子晶体施加单轴拉伸应力所产生的应变呈线性关系.该滤波器结构简单、可调谐性好, 在一系列精巧的光子晶体激光器、波分复用器或者其他精密仪器的制造中有一定的应用价值.     

Fabrication of two-dimensional organic photonic crystal filter

A high quality two-dimensional photonic crystal filter made of polystyrene is fabricated by the method of focused ion beam etching. Scanning electron microscopy (SEM) and transmittance spectrum are used to characterize the properties of photonic crystal filter. The measured transmittance spectrum is in agreement with the theoretical one. It is found that the filtering properties of photonic crystal filter, including the position and quality factor of optical channel, can be tuned by adjusting the width of line defect. PACS 42.70.Qs; 61.46.+w; 81.15.-z     

Terahertz wave narrow bandpass filter based on photonic crystal

We designed a narrow bandpass terahertz wave filter using photonic crystals with a line defect. An inserted linear defect in one-dimensional photonic crystal structures for a channeled filtering in the terahertz range are studied and designed theoretically. By using transfer matrix method, we examined the transmittance spectra for the proposed terahertz wave filter has a 3 dB transmission loss bandwidth of 20 MHz ranging from 0.29998 THz to 0.30001 THz. The simulated results show that a very narrow transmission band and high transmission (higher than 99.99%) centered at λ₀, and very sharp edges can be achieved.     

Plasma photonic crystals numerical and filter characteristics analysis based on symplectic algorithm

From the Maxwell equation, the method of symplectic finite-difference time-domain is applied in analyzing one-dimensional plasma photonic crystal. The propagation process of electromagnetic pulse in one-dimensional vacuum plasma photonic crystal structure is simulated by symplectic algorithm discrete in 2nd order time 2nd order space (T2S2), and 2nd order time 4th order space (T2S4) respectively. Then, from the perspective of frequency domain, the reflection coefficient of the plasma–vacuum photonic crystals is analyzed. The results show that the symplectic finite-difference time-domain method is accuracy and correctness. In the end, the filter characteristics of the plasma photonic crystals (PPCs) are analyzed in different thickness of plasma.     

一维缺陷光子晶体温度的测量

采用Si和SiO₂两种介质材料构造一维缺陷光子晶体,缺陷层介质为Si,利用传输矩阵法对带有缺陷的一维光子晶体的传光特性进行了理论分析,并得到其带隙特性.由于缺陷的存在,使得光子晶体的透射谱中产生缺陷峰.当被测温度变化时,根据两种介质的热光效应和热膨胀效应,光子晶体介质和缺陷层的光学厚度和折射率发生变化,透射谱缺陷峰产生漂移,由缺陷峰的中心波长漂移量得到被测温度的大小.构建了一维缺陷光子晶体测量温度的实验系统,实验结果表明缺陷峰中心波长与光子晶体所受的温度呈线性关系,测量灵敏度为0—2 关键词： 温度测量 一维光子晶体 传输矩阵法 缺陷峰     

Graphene based photonic crystal optical filter: Design and exploration of the tunability

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.     

基于磁光子晶体的低损耗窄带THz滤波器

本文提出一种采用石榴石型铁氧体磁性材料的太赫兹滤波器,利用波导线缺陷和腔内点缺陷的耦合特性,通过改变腔内介质柱半径及分布,实现对某个波长的耦合,达到了高效率滤波的功能;改变外磁场的大小,影响铁氧体材料的磁导率变化,使谐振频率发生改变,从而对THz波进行滤波.应用平面波展开法(PWM)和时域差分有限法(FDTD)进行仿真分析,研究结果表明,该滤波器其插入损耗为0.0997 d B,3 d B带宽为8.22 GHz,实现了低损耗窄带滤波.     

光子晶体超窄带滤波器

本文利用光学传输矩阵法研究了一种类似于谐振腔结构的光子晶体.研究发现在这种光子晶体的光子带隙的中央存在一个极窄的透光窗口,窗口的宽度在红外波段1500nm附近可以做到0.0001nm以下,窗口内的透光率峰值可以接近100%,窗口以外的区域的透光率可以做到0.01%以下.通过改变所研究结构中的周期厚度、中间夹层厚度、两边光子晶体的周期重复数和波的入射角可以改变窄带透过窗口的位置和窄带的宽度.这种光子晶体可以用来制作超窄带滤波器,有望在光通信超密度波分复用技术和光学信息精密测量技术当中获得应用.     

Optimal Design of Thin Film Filters for IR Integrated Photonic Amplifiers

This paper addresses in the design of thin film filter for IR broadband integrated photonic amplifiers. A cascaded multilayer medium thin film filter structure is presented. This proposed filter consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with finite difference time-domain(FDTD)-based overlapping integral-Runge Kutter(RK) method. The effect of transmittance spectrum of the proposed cascaded multilayer medium thin film filter on flattening gain is discussed. The transmission function of the cascaded multilayer medium thin film filter is obtained. Finally, a real device is fabricated, it is shown that the design is valid.     

基于磁化等离子体缺陷层的一维新颖可调谐的光子晶体滤波特性

将磁化等离子体填充到一维光子晶体的缺陷层,构成了一种新颖可调谐的滤波器。讨论了TM波情况下滤波器的滤波特性,并推导了TM波下磁化等离子体传输矩阵。通过改进的传输矩阵方法分析得到:在不改变光子晶体结构的情况下,通过改变等离子体频率和外磁场可以实现滤波通道在光子禁带内较大带宽范围的移动,同时禁带中滤波通道出现的数目也能被等离子频率与外磁场的大小控制。     

Comparison of photonic crystal narrow filters with metamaterials and dielectric defects

The photonic band-gap of the two kinds of 1D photonic crystal structure which is composed of the form of (AB) ^N1 C ^m (BA) ^N2 , one with a metamaterial defect layer (MDL) and the other one with a dielectric defect layer (DDL) are studied. Our results show that in both cases, where there is only one defect layer, m=1, no defect mode exists, but for two defect layers (m=2) there is a single defect mode which is centered in the middle of the band-gap. The width of the defect mode in DDL is narrower than that in MDL. For a number of defects of more than two (m>2) and even, in both of the MDL and DDL structures, there is only one defect mode. For m>2 and odd, the defect mode in the MDL vanishes, but for DDL there is two defect-mode symmetrically centered in the middle of the band-gap. The effects of the defect layers refractive index value, the periodicity number of the structures and the incident angle on the properties of the defect modes and the transmittance spectrum are discussed.     

Omni-directional reflection bands in one-dimensional plasma dielectric photonic crystals

In this paper the omni-directional reflection bands in one-dimensional plasma photonic crystal (PPC) have been studied theoretically. We present the study of plasma photonic crystal, having alternate regions of plasma?dielectric (Al₂O₃ or ZnS). Reflectances from this periodic multilayered structure in TE- and TM-modes are calculated for different angles of incidence in microwave region for omni-directional reflection bands. The reflectance is obtained by solving a Maxwell's equation using a translational matrix method. In addition to this, we have also studied the effect of variation of plasma width as well as plasma density on the reflection properties of plasma dielectric photonic crystal in TE- and TM-modes. The study of reflectance bands of such plasma photonic crystals shows that it can be used as omni-directional reflector.     

Study on modulation of near infrared radiation based on plasma photonic crystal

In this paper, a plasma photonic crystal (PPC) for infrared radiation modulation which is composed of indium tin oxide (ITO) and plasma is proposed. The performance of plasma photonic crystal in near infrared radiation modulation is researched by transfer matrix method (TMM). The simulation results show that the near infrared radiation pass band can be adjusted by the changing of plasma frequency of plasma. The reflection to near infrared radiation by plasma photonic crystal increases with plasma frequency and that of absorption decreases. In addition, the modulation performance of the plasma photonic crystal at different incidence wave angles is also studied. The results show that the incident wave angles have little effect on the transmission of plasma photonic crystal in near infrared band. The reflection of the plasma photonic crystal to near infrared radiation decreases with increasing of the incident wave angle, but that of the absorption increases with the incident wave angle. Therefore, the proposed plasma photonic crystal has a potential application in tunable near infrared filter devices.     

时变磁化等离子体光子晶体光子局域态分析

采用磁化等离子体的分段线形电流密度卷积(Piecewise Linear Current Density Recursive Convolution,PLCDRC)时域有限差分(Finite-Different Time-Domain,FDTD)算法研究了具有单一缺陷层一维时变磁化等离子体光子晶体的光子局域态特性。以高斯脉冲为激励源,用算法公式所得的电磁波透射系数来讨论了等离子体上升时间对其缺陷模的影响。结果表明,改变等离子体上升时间和密度可以获得不同的缺陷模。     

对称型单负交替一维光子晶体的能带结构

构造了(AB)^N(BA)^N对称型两种单负材料交替一维光子晶体,利用传输矩阵法进行数值模拟.结果表明：这种单负交替对称型一维光子晶体具有一种特殊带隙结构,该带隙不敏感于入射角和晶格的无序性.在该带隙内出现了两个隧穿模,该隧穿模不敏感于入射角的改变和晶格的无序性,但能带及带隙内的隧穿模却敏感于晶格标度和周期数的变化;随着入射角的改变,带隙两侧的隧穿模趋于简并.这些特性对在利用此结构光子晶体设计双重超窄带滤波器时,具有一定的参考价值. 关键词： 光子晶体 单负材料 光子带隙     

Saturable and reverse saturable absorption of a linear polymer in dimethylformamide

An all-optical tunable narrow-band filter with an ultrafast response time of 10 ps is realized in a two-dimensional nonlinear polystyrene photonic crystal. The pump and probe scheme is adopted to measure tunability based on the picosecond optical Kerr effect. The passband of the photonic crystal filter shifts about 4 nm under excitation of 14.7 GW/cm² pump intensity, which is in agreement with the theoretical prediction. PACS 42.70.Qs; 61.46.+w; 81.15.-z     

对称双缺陷光子晶体的可调谐滤波特性分析

基于光子晶体的光子局域特性,并利用光子晶体的介观压光效应,提出了一种新型的双通道可调滤波器结构.采用传输矩阵法对该滤波器的光学传输特性进行了理论推导,建立了透射谱与光子晶体结构参数的关系,讨论了介观压光效应对双缺陷光子晶体透射谱的影响,并对所设计的光子晶体结构进行了数值模拟.结果表明:随着入射角度的增大,缺陷峰发生蓝移.随着各介质层折射率或几何厚度的增加,缺陷峰发生红移.当光子晶体发生轴向拉伸应变时,缺陷峰的位置向长波长移动,但缺陷峰的峰值大体不变,从而验证了此滤波器的可调节性.该光子晶体滤波器结构紧凑,可调谐性好,为光子晶体激光器及传感器的设计提供了一定的理论参考.