几种新型可调谐窄带光滤波器

本文介绍了按常规光器件制作工艺可实现的几种新型可调谐窄带光滤波器的原理及性能，简单分析了各自的功能特点与不足。     

Proposal for Compact Optical Filters Using Large Index Step Binary Supergratings

Compact optical filters are proposed using an aperiodic grating of fixed element size [i.e., a binary supergrating (BSG)] with a large refractive index step. These filters allow for almost arbitrary wavelength filtering, yet they are more compact than previous demonstrations of BSG. The filters are designed using a combination of Boolean particle swarm optimization (B-PSO) and a one-dimensional transfer matrix method. To demonstrate the compact device size, several 50-mum-long single-wavelength transmission filters are demonstrated theoretically, each having a different wavelength while using the same structural parameters. A multiwavelength filter is also proposed in an 80-mum-long structure to show the versatility of the large refractive index step BSG. A genetic algorithm is substituted for the B-PSO; however, B-PSO shows better performance here. This work may be applied to produce compact optical filters for intrachip optical networks and compact tunable lasers, while using existing single-step photolithography processes.     

纯相位二值化匹配滤波器的优化设计

通过采用神经网络中的Clipping方法和MonteCarlo修改学习算法,对用于光学模式识别的纯相位二值化匹配滤波器进行了优化设计。计算机模拟结果表明,和传统的纯相位匹配滤波器的相关输出结果相比,其识别输出的信噪比和信号相关峰值得到了明显的提高,从而为今后的光学实现奠定了良好的基础。     

Design and Modeling of a Nanomechanical Sensor Using Silicon Photonic Crystals

Conventionally a line defect in the photonic crystal (PhC) is used to create a waveguide for light propagation through the PhC. A PhC based filter is designed by introducing micro-cavities within the line defect so as to form the resonant bandgap structure for PhC. Such a PhC waveguide (PhCWG) filter shows sharp resonant peak in output wavelength spectrum. We proposed a suspended silicon bridge structure comprising this PhCWG filter structure. Since the output resonant wavelength is sensitive to the shape of air holes and defect length of the micro-cavity. Shift of the output resonant wavelength is observed for suspended PhCWG beam structure under particular force loading. In other words, the induced strain modifies the shape of air holes and the spacing among them. Such an effect leads to shift of resonant wavelength. Under optical detection limitation of 0.1 nm for resonant wavelength shift, the sensing capability of this nanomechanical sensor is derived as that vertical deformation is 20-25 nm at the center and the smallest strain is 0.005% for defect length. This innovative design conceptualizes a new application area for PhCs, i.e., the nanometer-scale physical sensors for strains and forces.     

PAM Pulse Generation Using Binary Transversal Filters

Modern narrow-band pulse-amplitude modulation (PAM) and pulse-code modulation (PCM) systems require the generation of precisely shaped pulses in order to avoid intersymbol interference. It is not a simple matter to design analog filters having pulse responses with the requisite carefully positioned zeros, and this has led researchers to study other approaches. It is shown that the use of a binary transversal filter (BTF) coupled with a simple low-pass filter can generate extremely good pulses with small bandwidths. A BTF consists of a digital shift register and weighting resistor network to construct a staircase approximation to the desired pulse. The attendant circuitry is very simple, such that a highquality pulse generator can be built and adjusted with remarkable ease. The problem of pulse design using BTF's is considered in some generality, and a computational procedure is developed for adjusting the weighting network in the BTF to generate optimum pulse shapes. This method is then applied to several practical cases, and the circuitry required to generate excellent pulses is discussed. Test results on an implementation of such a generator using only five taps are presented, revealing the inherent simplicity and quality of the approach.     

基于金属亚波长光学结构窄带滤色片的研究进展

窄带滤色片是一种在可见光波段选择性地反射或者透射特定波长的可见光而呈现不同颜色的常用光学元件,在液晶显示、光通信、传感探测和成像等多个领域得到广泛应用。综述了金属亚波长光学结构窄带滤色片的研究进展。根据结构形式的不同,将金属亚波长窄带滤色片进行了划分,主要包含了平直金属亚波长薄膜结构、金属-介质-金属腔结构、金属孔或颗粒阵列结构、金属光栅与其他结构组成的复合结构等类型。依次总结出了这些不同类别金属亚波长窄带滤色片器件的工作原理及近些年来所取得的研究进展。此外,还介绍了基于Fano共振原理的金属亚波长窄带滤色片,这类器件可以实现半峰全宽小于10 nm的超窄带滤色效果。     

光子晶体增益平坦滤波器的设计

掺铒光纤放大器(EDFA)的增益平坦化是波分复用(WDM)系统中的重要问题.提出了用光子晶体实现增益平坦的新方案.通过分析EDFA增益平坦的原理与一维光子晶体的反射谱(在不同波长处具有不同反射率的特性),设计出了满足特定条件的增益平坦滤波器.以EDFA典型曲线为例,利用遗传算法简便精确地优化一维光子晶体的周期数,从而设计出了与EDFA增益谱相匹配的增益平坦滤波器.结果表明,级联的一维光子晶体滤波器在1530～1560 tim范围内对EDFA的增益进行平坦,且不平坦度约为±0.6 dB.     

Recent Advances Toward Optical Devices in Semiconductor-Based Photonic Crystals

Photonic crystals, artificial, wavelength-scale multidimensional periodic structures, have given birth to a number of realizations in semiconductors. Photonic integrated circuits, especially around new integrated lasers, are challenging directions of research for miniaturization and new functions in optical telecommunications. We review the basic physics behind such applications and underline the current status of this very active research field worldwide.     

光子晶体光学频率变换技术

文章首先介绍了光子晶体光学频率变换技术的基本原理和技术特点;然后简述光子晶 体光学频率变换技术研究进展情况;最后指出了光子晶体变频技术在可调谐激光器和其它领域中的应用前景。     

Bending Loss Analysis of Optical Fiber with Out-Cladding of Photonic Crystals

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基于Thue-Morse序列准周期光子晶体的全光二极管现象

利用传输矩阵法研究了Thue-Morse序列准周期光子晶体的传播特性。线性结构的共振谱具有自相似的分形结构,共振模在晶体中的电场分布也具有类似的自相似结构。对于具有Kerr非线性的奇数阶Thue-Morse序列结构,由于其内部电场分布的不对称性,可以导致正反向入射时不同的双稳态现象。通过额外的抽运光激励,可以实现某光强的光单向透射,使得结构真正体现全光二极管的功能。     

Multitap Photonic Microwave Filters With Arbitrary Positive and Negative Coefficients Using a Polarization Modulator and an Optical Polarizer

A novel multitap photonic microwave filter with arbitrary positive and negative coefficients implemented using an electrooptic polarization modulator (PolM) and an optical polarizer is proposed and experimentally demonstrated. In the proposed filter, the optical polarizer is connected at the output of the PolM with its transmission axis aligned at an angle of 45 to one principal axis of the PolM. By adjusting the polarization direction of the input lightwave to be 45 or 135 to one principal axis of the PolM, an inverted or noninverted intensity-modulated optical microwave signal is obtained at the output of the optical polarizer, which leads to the generation of a negative or positive coefficient. A time delay difference between adjacent taps is generated by using a wavelength-dependent delay line. A five-tap photonic microwave filter with arbitrary positive and negative coefficients is demonstrated. The reconfigurability of the filter is also investigated.     

Porous Supramolecularly Templated Optical Resonators Built in 1D Photonic Crystals

A synthetic route to attain photonic multilayers that presents controlled porosity only at the middle‐layer level is shown. The spectral resonance associated with this porous layer shows strong sensitivity to the presence of vapors adsorbed or condensed within the void network, providing a potentially relevant material for gas detection. The importance of the interplay between pore and probe‐molecule diameters is studied and its implications in size‐selective detection are discussed.     

基于金属亚波长光学结构窄带滤色片的研究进展(续)

<正>3金属孔或颗粒阵列的窄带滤色片基于金属阵列结构的窄带滤色片最为常见,除了前述金属-介质-金属腔阵列结构以外,基于金属孔阵列、金属颗粒阵列以及金属孔与颗粒的复合阵列均可实现窄带滤色性能,尤其是有关金属孔阵列滤色片的报道最为广泛。3.1金属孔阵列的窄带滤色片金属孔阵列(图10 (a))在特定波长下的超常透射行为最早由T.W.Ebbesen等人[60]于1998     

一种具有光放大功能的滤波器设计

设计了包含缺陷层和多层异质结构的混合结构的一维光子晶体,然后在光子晶体中加入泵浦源.用传输矩阵法研究了加入泵浦源前后光子晶体的透射谱,结果发现该混合结构的光子晶体具有非常宽周且平坦的禁带,且在此禁带内只有一条极窄的透射带,加入激励源后的透射带透射率远远大于1,并且透射带的透射率和位置都可以通过调节光子晶体的参数来改变.利用这些特性,设计了一种具有放大功能的宽禁带超窄单通滤波器,当激活系数取0.033 4时,在1000～2000 nm的禁带范围内只有在红外波段1550 nm处出现一条透射率为1.1×106,3 Db带宽为0.005 nm的透射窄带.     

一维三元光子晶体的传输特性研究

运用光学传输矩阵理论对一维三元光子晶体传输特性进行了数值计算。结果表明,其带隙宽度随结构参数α、b明显的改变;适当调节两个参数,得到了带隙相对宽度(△ω/ω0)为68％的带隙结构,带隙宽度几乎不随入射角的变化而改变,并且随实际操作中带来的随机误差引起的无序度的改变不明显,由此可方便地用于制作全角宽带反射镜等光学器件。     

窄带FBG滤波器切趾函数的研究

利用耦合模理论分别对五种切趾函数所描述的窄带光纤光栅滤波器的滤光特性进行了数值计算,通过比较得到一些有意义的结论,为设计和制作窄带光纤光栅滤波器提供了参考和理论依据.     

光子晶体与光子晶体光纤的应用

介绍了上世纪80年代末出现的光子晶体的概念和材料特点、光子晶体光纤的性能、国际学术界的研究热点及具有深远影响的应用领域。     

Design and Analysis of Ultra-Miniaturized Meandering Photonic Crystals Delay Lines

In this paper, we study the characteristics of a novel miniaturized optical delay line, which delays light in a meandering photonic crystal waveguide, and describe the design steps. We show how lattice parameters and refractive index difference of the photonic crystal affect the bandgap width and suggest a criterion to select these parameters. Next, we focus on the parallel waveguide channels in photonic crystal, and analyze the impact of the channel length and the interchannel spacing on crosstalk. We suggest a method for mitering the sharp corners in meandering lines which reduces the undesired reflections by 8 dB. Considering all these guidelines, we examine the propagation of light in the proposed delay line through calculating time-delay and insertion loss. To achieve longer delays in a small device area, we concentrate on coupled cavities in photonic crystals and propose an approximate method for calculating the group velocity of light in the coupled defects. We show how by replacing waveguide channels of a meandering delay line with coupled defects we achieve time-delays more than 9 ps within a device size around 27 m, which corresponds to a miniaturization factor of 100.