Trapezoid 2D photonic crystal nanoring resonator-based channel drop filter for WDM systems

In the present work, a nanostructure of trapezoid photonic crystal ring resonator-based channel drop filter is designed for wavelength division multiplexing systems (WDM) to drop a channel at a center peak wavelength of 1543 nm. The proposed channel drop filter is composed of bus waveguide, drop waveguide, trapezoid nanoring resonator and reflector in a two-dimensional (2D) hexagonal lattice with circular rods arranged in air host. The trapezoid nanoring resonator is playing a very important role in WDM systems for dropping a single channel over a wide wavelength range. The photonic band gaps of perfect lattice structure and non-perfect lattice structure are absolutely calculated by plane wave expansion method. The functional properties of the designed filter are evaluated by finite difference time domain method (FDTD). The functional properties are center peak wavelength, dropping efficiency, passband width and quality factor. The FDTD method results show dropping efficiency is 100%, and quality factor is about 514.33 which are highly suitable for WDM systems. Further, lattice constant, inner and outer rod radius and refractive index difference of the structure are varied to tune the filter center peak wavelength and its corresponding functional parameters effects are investigated. The proposed nanoring resonator-based optical filter is ultra-compact size around \(14\, \upmu \hbox {m} \times 8.4\, \upmu \hbox {m}\); hence, it is extremely suitable for WDM-based photonic communication systems and photonic integrated circuits.     

Two-dimensional photonic crystal ring resonator-based channel drop filter for CWDM application

In this paper, a channel drop filter based on two-dimensional photonic crystal ring resonator (PCRR) is proposed. The proposed structure consists of bus waveguide, dropping waveguide and a ring resonator. We have focused on improving the dropping efficiency and quality factor of the structure by applying different optimization techniques. Optimized channel drop filter using PCRR is designed, and it is extended to drop three different channels by changing the inner rods radius in each ring resonator that act as a demultiplexer. As designed structure drops three different channels such as 1524, 1544 and 1565 nm, the band gap for the structure is calculated and observed by plane-wave expansion method. The normalized transmission spectra and resonance wavelengths for different radius are obtained using two-dimensional finite-difference time-domain method. The proposed PCRR-based demultiplexer has the channel spacing of about 20 nm which fulfils the requirements of coarse wavelength-division multiplexing systems. The size of the demultiplexer is small; hence, it can be utilized for photonic integrated circuits.     

带反射腔的光子晶体分插复用器

提出一种由二维光子晶体构成的四端口滤波器。该滤波器含三个微腔,其中两个是参数完全相同的波长选择性反射腔,用于波长选择性的反射反馈。另外一个是下载腔,用于下载特定的波长光波。利用耦合模式理论（CMT）分析了该滤波器的滤波特性,得出了实现完全下载滤波的条件,即通过改变两波长选择性反射腔到下载腔之间的距离,使之满足晶格周期的奇数倍。并且用FDTD方法对该器件进行了数值分析,显示了该器件上下载的的可行性。     

A high-drop hole-type photonic crystal add-drop filter

Based on the effect of total internal reflection（TIR）and photonic band gap,a new type of hexagonal-lattice hole-type silicon photonic crystal add-drop filter is proposed with a large circular hole as inner ring.The single mode operation is realized by compressing the two rows of photonic crystal above and below the line defect waveguide.Two-dimensional（2D）finite-difference time-domain（FDTD）method is then applied to investigate the impacts of side length of inner ring and coupling strength on its drop efficiency.It is also fairly compared with the traditional inner ring structure composed of hexagonal-lattice holes.The results show that the proposed structure can offer higher spectral selectivity than the traditional one.Two channel wavelengths of 1.425μm and 1.45μm can be simultaneously dropped at corresponding ports with drop efficiency of more than 90%and quality factor of 900 in the proposed configuration when the width of bus waveguide,the side length of inner ring and the coupling strength are 0.8 3 a,4a and 0,respectively,where a is the lattice constant.     

Photonic crystal add–drop filter: a review on principles and applications

Add–drop filter (ADF) is a key component in optical integrated circuits that can be used in all-optical communication networks and wavelength division multiplexing (WDM) systems. The quality factor, coupling efficiency, transmission efficiency and coupling length are important parameters in add–drop filters. Photonic crystal (PC) optical devices have become popular among researchers because their structure is suitable to embed into optical circuits. This paper covers a comprehensive review of the principle structure of ADF, coupled mode theory (CMT), types and recent applications in WDMs, accelerometer and bio/chemical sensors. Although there are some different categories of photonic crystal ring resonator-based ADF in general, all of them can be divided into photonic to two class of non-circular and circular. This article is reported a comprehensive study about ADF and improvement of these ADF.

     

基于二维光子晶体带隙及自准直效应的光分插滤波器研究

鉴于光子晶体具备控光能力强和响应速度快等优点,设计了基于二维光子晶体带隙及自准直效应的光分插滤波器。将二维的正方晶格介质柱当作材料,并融合光子晶体带隙、自准直效应实现光分插滤波器设计。引入平面波展开法,实现完整周期光子晶体架构求解。引入时域有限差分法,获取晶体中的电场磁场整体分布。模拟结果显示,该结构耦合效率与品质因子良好,且场图模拟与对应结构透射谱拟合度较高,表现出了较强的可实践性。     

Asymmetrically coupled silicon-on-insulator microring resonators for compact add-drop multiplexers

We report on improved filter characteristics of microring resonators (MRs) used as add-drop multiplexers for integrated photonic circuits. By introducing an asymmetrical coupling of the signal waveguides to the resonator, a higher throughput attenuation and drop efficiency is attained. The throughput attenuation is the decisive property for the application of microrings in photonic networks since it determines the crosstalk between drop signal and add signal at the throughput channel of an add-drop multiplexer. Experimental results are compared with analytical relations. MRs with a free-spectral range of 24 nm are fabricated on silicon-on-insulator substrates. A crosstalk reduction by 8.8 dB due to asymmetrical coupling is demonstrated.     

Ultra-compact optical filter in two-dimensional photonic crystal

A design of an ultra-compact in-plane optical add/drop filter is proposed. The filter is formed by two waveguides and one two-mode cavity in a two-dimensional triangular photonic crystal. The simulated results demonstrate good transfer characteristics with a quality factor of about 1700.     

Ultra-high-Q optical filter based on photonic crystal ring resonator

In this study, a photonic crystal ring resonator with a triangular lattice is used to design an optical filter. The proposed structure is able to filter the central wavelength of 1548 nm with a transmission coefficient of over 95%. Moreover, this structure has an ultra-high-quality factor (Q) of about 1290. With altering the features of the structure including the refractive index, the lattice constant and the radius of the rods in the resonator core, their effects on the central wavelength of the filter, transmission coefficient, quality factor and bandwidth are investigated. The plane wave expansion and finite-difference time-domain methods are used to extract photonic band gap and investigate the photonic behavior of the proposed structure, respectively.     

Channel drop filter using a single defect in a 2-D photonic crystal slab waveguide

This paper describes a theoretical and experimental analysis of the channel drop filter using a single defect formed near the two-dimensional (2-D) photonic crystal slab waveguide. First, we calculate the transmission spectrum of a 2-D photonic crystal waveguide and show that high transmittance for a wide wavelength range (/spl sim/60 nm) is obtained in the 1.55-/spl mu/m region. We also show that a defect state having a wavelength within the high transmission wavelength range can be formed in the photonic bandgap by introducing a single defect of appropriate radius. Next, we fabricate several devices and show that the emission wavelength from each defect can be tuned by changing the defect radius. The measured tuning characteristics coincide well with the calculated results. From the near-field pattern of the device, we estimate the emission efficiency of the present device at almost a few tens percent. We clarify the structural condition in order to obtain the maximum output efficiency and show that tuning of emission wavelength while maintaining high output efficiency is possible by selecting appropriate defect radius and position. Based on these results, we propose an ultrasmall channel drop filter for a wavelength-division-multiplex optical communication system.     

Microwave Correlator Based on a Nonuniformly Spaced Photonic Microwave Delay-Line Filter

We propose and demonstrate a novel technique to perform matched filtering of a phase-coded microwave signal using a photonic microwave delay-line filter. The photonic microwave delay-line filter is designed to have a frequency response that is conjugate to the spectrum of the phase-coded microwave signal. To implement the delay-line filter, the tap coefficients are usually complex, which is difficult to implement in the optical domain. In this letter, a photonic microwave delay-line filter with equivalent complex coefficients implemented using an all-positive- coefficient photonic microwave delay-line filter based on a nonuniformly spaced delay-line structure is proposed. Since only positive coefficients are required, the implementation of the filter is greatly simplified. An experiment is performed. The decoding of a 6.75-GHz binary-phase-coded microwave signal is experimentally demonstrated.      

Photonic crystal ring resonator based add-drop filter using hexagonal rods for CWDM systems

In this paper,theoretical analysis of two-dimensional photonic crystal ring resonator(2D PCRR) based add-drop filter(ADF) is presented for coarse wavelength division multiplexing(CWDM) system to drop a channel at 1511 nm using hexagonal rods that are positioned in the square lattice.The 2D finite difference time domain(2D FDTD) method and plane wave expansion(PWE) method are used for obtaining the filter response and band structure of the filter respectively.Close to 100 dropping and coupling efficiencies at 1511 nm and 16 nm of bandwidth are observed through simulation.This is very well meeting the requirement of ITU-T G.694.2 standard,which is specified for metro access and short haul optical networks.The overall size of the proposed filter is 11.4 μm×11.4 μm.It can also be used in integrated optics.     

基于内全反射微环空气孔型光子晶体光分插滤波器

提出一种基于内全反射微环和光子晶体带隙相结合的混合结构空气孔型二维三角晶格光子晶体光分插滤波器,通过压缩及移位围绕线缺陷波导的上下两排光子晶体阵列,实现空气孔型线缺陷波导单模的有效调控,进而影响信道的下路效率,并且利用二维时域有限差分法系统分析不同波导宽度以及不同移位量δ时滤波器的下路效率。模拟计算表明,当波导宽度为0.8槡3晶格常数,耦合强度为0个晶格常数,移位量为0.5个晶格常数,信道波长为1464nm时,下路效率为-0.11dB,品质因子Q为1100;当波导宽度为0.8槡3晶格常数,耦合强度为1个晶格常数,移位量为0个晶格常数时,下路效率为-0.89dB,品质因子Q为2100。     

光子晶体与光子准晶复合型上下载滤波器

基于二维正方晶格光子晶体与十二重Stamfli型光子准晶提出了单环形腔上下载滤波器及双环形腔串联上下载滤波器.分析并对比了两种上下载滤波器的传输效率随光子准晶介质柱半径及折射率大小的变化规律,且对比了两种上下载滤波器的品质因数随环形腔中心介质柱半径及折射率大小的变化规律.结果表明,双环形腔串联复合型上下载滤波器的性能优于单环形腔复合型上下载滤波器.研究结果将为设计及制备优良上下载滤波器件提供一定指导作用.     

A high quality factor photonic crystal channel-drop filter with a linear gradient microcavity

We design a channel-drop filter (CDF) with a linear gradient microcavity in a two-dimensional (2D) photonic crystal (PC). The model of three-port CDF with reflector is used to achieve high quality factor (Q-factor) and 100% channel-drop efficiency. The research indicates that adjusting the distance between reference plane and reflector can simultaneously influence the Q-factor due to coupling to a bus waveguide and the phase retardation occurring in the round trip between a microcavity and a reflector. The calculation results of 2D finite-difference time-domain (FDTD) method show that the designed filter can achieve the drop efficiency of 96.7% and ultra-high Q-factor with an ultra-small modal volume.     

太赫兹光子滤波器技术的研究

太赫兹技术具有分辨率高、穿透力能力强等优点,正逐步成为军事和民用领域的研究热点。介绍了工作于太赫兹波段的光子滤波器的工作原理,推导了光子滤波器的传递函数,在此基础上设计了一种新型的基于级联调制器的光子滤波器结构,利用Optisystem构建了传统光子滤波器和级联调制器的光子滤波器的仿真模型,并进行了对比仿真和分析。研究发现滤波器的品质因数Q和掺铒光纤放大器的最大输出功率有直接关系,基于级联调制器的光子滤波器具有更好的滤波特性。     

Design and characteristics of a novel narrow-band filter with the dual-core photonic crystal fiber

A novel narrow-band filter based on the dual-core doped photonic crystal fiber is proposed. By optimizing structure parameters of the photonic crystal fiber, the index curves of the fundamental modes for the two cores are crossed at 1.55 μm and the wavelength-selective coupling is achieved. The characteristics of the filter are numerically simulated by the full-vector beam propagation method. And the simulation results show that the coupling length and the bandwidth of the filter are 16.4 mm and 9 nm at −3 dB loss, respectively. It demonstrates the advantages of the filter with a small size, a low transmission loss and the narrow-band width.     

光子晶体齿状波导的滤波特性研究

为了设计基于光子晶体波导的高性能滤波器件,在2维正方格子光子晶体波导结构中引入一系列齿状缺陷,采用有限元法对齿状光子晶体波导的传输特性进行了数值仿真和理论分析。结果表明,对于单个齿状缺陷,缺陷产生的共振频率使得在光子晶体波导通频域带出现带隙结构,可以实现良好的窄带滤波,并且通过改变齿状缺陷深度可以有效地控制缺陷的共振频率;引入多个齿状缺陷,缺陷之间会经过耦合作用形成一系列缺陷态,使得在光子晶体波导导通频域中出现宽带的带隙结构,可以实现宽带滤波。该光子晶体波导滤波器对窄/宽带滤波可根据波导结构中引入的齿状缺陷进行简单灵活调节。此研究在设计基于光子晶体波导的光子滤波器件方面具有潜在的应用价值。     

FIR Photonic Microwave Filter Design Employing Simulated Annealing Algorithm

Photonic microwave filters are important parts of fiber‐optic microwave/millimeter wave processing systems. In this paper, the synthesis problem of fiber‐optic FIR microwave filters is addressed and a novel method for designing photonic microwave filter employing a simulated annealing (SA) algorithm is proposed. The design problem of photonic microwave filter can be reduced to be a multi‐variable function optimization problem, which can be solved by a simulated annealing‐based algorithm. As an illustration of the application of SA to photonic microwave filter design, the synthesis of an optimizedFBG‐based photonic microwave filter is discussed. Numerical results show that the global minimum finding capability of SA makes it be an efficient way to design the photonic microwave filter. Numerical results also demonstrate that the proposed method can be applied to design different filtering systems with different constraints.     

新型光子晶体四通道滤波器研究与设计

基于光子晶体环形腔缺陷与线缺陷波导之间的共振耦合原理,设计了 一种由新型环形腔和主波导组成的四通道二维三角晶格光子晶体滤波器.运用平面波展开法和时域有限差分法分析了光波在整合结构中的传输特性,并进一步讨论环形滤波器内的内部介质柱半径大小对滤波器传输特性的影响.结果表明:新改进环形的滤波器传输效率达到80％左右.通过实验...