用金属小球进行长波量子阱红外探测器的光耦合

针对实验中9.5μm峰值响应波长的n型长波量子阱红外探测器设计运用二维金属小球(铜)阵列作光耦合结构.金属小球阵列均匀填充在绝缘的胶黏剂中，基于惠更斯原理研究二维金属小球阵列体系的光耦合和光吸收，结果表明对9.5μm响应波长的长波量子阱红外探测器，采用周期为3μm，半径为0.9μm左右的金属小球阵列可以获得最佳的光耦合.优化设计后的量子效率(66%)远高于45°磨角耦合的量子效率(38%)，为实验运用金属小球阵列进行长波量子阱红外探测器的光耦合提供了基本的理论依据和详细的优化设计方案.     

两端叠层结构的中长波量子阱红外探测器

采用分子束外延技术生长了两个叠层结构的双色量子阱红外探测器结构,并经过光刻和湿法刻蚀制作成两端结构的量子阱红外探测器单元器件. 通过改变量子阱势垒高度,势阱宽度,掺杂浓度,重复周期数等器件参数,可以使总电压在两个叠层之间产生适当的分布,从而使器件表现出不同的电压响应特点. 光电流谱测量显示,器件1随着外加偏置电压可实现对于中波大气红外窗口(3—5 μm)和长波大气红外窗口(8—12 μm)红外响应的切换,器件2在不同的偏置电压下可以对这两个波段同时做出响应. 本文探讨了两端叠层结构量子阱红外探测器的工作原 关键词： 电压调制 同时响应 量子阱红外探测器 双波段     

10—14 μm同时响应的双色量子阱红外探测器

实现截止波长为11.8和14.5 μm双色同时响应的量子阱红外探测器,可以同时工作在8—12 μm大气窗口和甚长波波段.在77 K下测量到很强的光电流谱.器件结构采取了较为简洁的设计,通过适当增大量子阱结构中势阱的宽度和选择合适的掺杂浓度,在同一偏压下实现了对两个波长的同时响应.两个光响应峰分别为基态到第五激发态和基态到第一激发态的跃迁吸收. 关键词： 量子阱红外探测器 双色 同时响应     

甚长波量子阱红外探测器光栅耦合的研究

采用平面波展开的散射矩阵方法研究n型甚长波量子阱红外探测器的二维衍射光栅，并同时从实验方面研究了其红外透射光谱.研究表明，n型量子阱器件的光栅耦合是传输场和倏逝场共同作用的结果.对于n型量子阱红外探测器的光栅耦合，光栅周期、光栅深度和占空比三者之间相互影响；要达到好的光学耦合效果，需要根据量子阱器件的峰值探测波长选择合适的光栅参数. 关键词： n型量子阱红外探测器 二维光栅 光耦合     

甚长波量子阱红外探测器的暗电流特性研究

基于载流子在量子结构中的输运理论研究了甚长波量子阱红外探测器(峰值响应波长15μm，量子阱个数大于40)的载流子的输运性质.研究结果表明，在甚长波量子阱红外探测器中，电流密度一般很低，暗电流主要来源于能量高于势垒边的热激发电子.通过薛定谔方程和泊松方程以及电流的连续性方程的自洽求解，发现外加偏压下电子浓度在甚长波器件各量子阱的分布发生较大变化，电场在整个器件结构上呈非均匀分布，靠近发射极层的势垒承担的电压远远高于均匀分布的情形.平带模型假定电压在器件体系上均匀分布，导致小偏压下的理论计算值远远低于实验值. 关键词： 甚长波量子阱红外探测器 量子波输运 暗电流     

基于表面等离激元的长波QWIP光栅优化

为了提高长波量子阱红外探测器的灵敏度及探测率,采用表面等离激元效应来提高量子阱红外探测器中二维光栅的耦合效率。利用三维时域有限差分算法,分析表面等离激元作用下,长波量子阱红外探测器中二维金属薄膜光栅参数对入射光的调制作用。计算结果表明,对于8 m的入射光,当光栅周期P=2.8 m,孔直径D=1.4 m,光栅层厚度L=0.04 m时,X Y平面内Z方向电场值最大,光栅的耦合效率最高。     

太赫兹量子阱光电探测器光栅耦合的模拟与优化

光栅耦合是量子阱光电探测器探测正入射电磁辐射的常用耦合方法,本文采用模式展开法研究了一维金属光栅太赫兹量子阱光电探测器中的电磁场分布,并给出了器件有源区中的平均光强.研究结果表明,若一维光栅的周期与太赫兹波在器件材料中的波长相当,并且根据器件结构选取合理的光栅占空比,可使器件中的平均光场最强,光栅的光耦合效率最高,从而提高器件的响应率. 关键词： 太赫兹 量子阱光电探测器 光栅     

具有新型有源区的量子级联探测器(特邀)

量子级联探测器是一种光伏型的子带间跃迁红外探测器,通过厚度渐变的啁啾量子阱中台阶状的子带分布,产生内建电场,使得有源区中的光生载流子定向输运,器件工作时无需外加偏压,避免了暗电流噪声的产生,能够实现室温长波红外响应。由于子带间跃迁吸收系数小、具有偏振选择性,量子级联探测器目前存在响应率低、对正入射响应无响应、探测率对温度敏感等问题。针对这些问题,本文介绍三种新型量子级联探测器有源区的设计,包括量子点/阱耦合、束缚-微带斜跃迁和小能量台阶有源区,在中波、长波和甚长波波段展现出优良的器件性能。     

GaAs/AlxGa1-xAs量子阱能级结构设计与光谱分析

通过理论计算对用于量子阱红外探测器的GaAs/AlxGa1-xAs量子阱能级结构进行模拟设计,将不同生长结构的量子阱材料的光响应谱和光致荧光谱(PL)与计算结果进行比较.说明量子阱生长结构与量子阱能级结构的关系.欲使量子阱红外探测器的响应峰值在8μm附近,则需量子阱结构中阱宽为47nm,垒中Al含量为029.理论计算与测试结果符合得较好. 关键词：     

量子阱红外探测器的光耦合

本文从有效质量近似理论出发,在量子阱导带内子带间光吸收分析的基础上,评述了ｎ型量子阱红外探测器的光耦合。着重研究适宜于量子阱红外探测器的不同种类的光栅,并从理论上优化出高耦合效率的各种光栅参数     

Two-dimensional photonic crystals with a lattice defect: Spectrum of defect modes, localization of light, and formation of evanescent waves

Properties of an electromagnetic field localized in the defect modes of two-dimensional photonic crystals are studied. The defect-mode spectrum of these structures is calculated, electromagnetic field localization and channeling effects are analyzed, and the properties of the field inside and beyond a photonic crystal with a lattice defect are also studied. The calculations show that the electromagnetic field is localized in the defect mode of a photonic crystal in a region smaller than the wavelength. The dependence of the defect-mode spectrum on the parameters of the photonic crystal is investigated and possibilities for controlling the spectrum of defect modes are indicated. It is shown that the optical field leaving a photonic crystal possesses the properties of a evanescent wave, which means that spatial resolution substantially greater than the wavelength of the radiation can be achieved in the near field and opens up possibilities for using photonic crystals with a lattice defect in near-field optical microscopy. The possibility of externally controlling an optical field localized in the defect modes of a photonic crystals is demonstrated.     

Negative refraction in two-dimensional photonic crystals

We present some of our recent results for negative refraction in photonic crystals. The concept of negative refraction in photonic crystals is firstly introduced. Then, the propagation of electromagnetic waves in photonic crystals is systematically studied. By the layer Korringa–Kohn–Rostoker method, the coupling efficiency between external plane waves and the Bloch waves in photonic crystals is investigated. It is found that the coupling coefficient is highly angular dependent even for an interface between air with n=1 and a photonic crystal with effective index n_eff=-1. It is also shown that, for point imaging by a photonic crystal slab, owing to the negative refraction, the influence of the surface termination on the transmission and the imaging quality is significant. Finally, we present results experimentally demonstrating negative refraction in a two-dimensional photonic crystal at optical communication wavelengths. PACS 42.70.Qs; 41.85.Ct; 42.30.Va     

微光栅对SiC/光子晶体结构热辐射特性的调控

本文研究了一种SiC薄膜/光子晶体结构的热辐射特性,在SiC薄膜/光子晶体的界面处具有微光栅结构。利用RCWA方法数值模拟了该结构的热辐射特性,发现在SiC薄膜/光子晶体的界面处由于不同的电磁模态激发,导致其发射率在多个频段或方向具有很高的值,从而可通过利用不同电磁模态激发的条件及其相互作用实现对热辐射的调控。     

Numerical Analysis of Coupling between Two-Dimensional Conventional Dielectric Waveguides and Photonic Crystal Waveguide

A problem of coupling between conventional dielectric waveguides and a two-dimensional photonic crystal waveguide is analyzed, using the Fourier series expansion method combined with the absorbing boundary condition of a perfectly matched layer (PML). A novel structure for the input and output ends of the photonic crystal waveguide is proposed to increase the coupling efficiency. Numerical examples are demonstrated and discussed to validate the effectiveness of the proposed structure.     

立体耦合光子晶体薄板微腔的高Q值特性研究

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.     

Experimental demonstration of self-collimation inside a three-dimensional photonic crystal

We present our experimental demonstration of self-collimation inside a three-dimensional (3D) simple cubic photonic crystal at microwave frequencies. The photonic crystal was designed with unique dispersion property and fabricated by a high precision computer-controlled machine. The self-collimation modes were excited by a grounded waveguide feeding and detected by a scanning monopole. Self-collimation of electromagnetic waves in the 3D photonic crystal was demonstrated by measuring the 3D field distribution, which was shown as a narrow collimated beam inside the 3D photonic crystal but a diverged beam in the absence of the photonic crystal.     

一维磁性光子晶体的电磁场分析和数值计算

本文探讨一维磁性光子晶体的概念和结构.提出了一种分析一维磁性光子晶体的法拉第旋转效应的电磁场方法.分析计算表明:嵌于光子晶体中的一层很薄的磁性材料将可获得比单独一层同样厚度的磁性材料大得多的法拉第旋转效应,从而从理论上验证了文献上的相关实验.同时也分析了一维磁性光子晶体用作光子晶体结构下的光隔离器等器件中的法拉第旋转器的可能.     

Ultra-strong light–matter coupling and superradiance using dense electron gases

The physics of the interaction between a dense two-dimensional electron gas and a microcavity photonic mode is reviewed. For high electronic densities, this system enters the ultra-strong coupling regime in which the Rabi energy, which measures the strength of the light–matter coupling, is of the same order of magnitude as the matter excitation. The ultra-strong coupling has been experimentally demonstrated by inserting a highly doped semiconductor layer between two metal plates that produce a microcavity, with extreme sub-wavelength confinement of the electromagnetic field. A record value at room temperature (73%) of the ratio between the Rabi and the matter excitation energies (the relative Rabi energy) has been measured together with a very large photonic gap induced by the polariton splitting. The ultra-strong coupling is a manifestation of a huge cooperative dipole, which is proportional to the number of electrons participating in the interaction. Such a phenomenal interaction with light appears also in the absence of a microcavity and, for a dipole coupled with free space, it gives rise to superradiance.     

Modeling of the propagation of single photons in finite one-dimensional photonic crystals

A model of the propagation of a quantized electromagnetic field in a one-dimensional photonic crystal that contains two-level atoms that interact with the field is proposed. The model separately considers the interaction of the quantized radiation with the quantum system and with the photonic crystal. The use of the model is exemplified by its application to the study of the decay of excited states of one- and two-level atoms placed in the photonic crystal. The possibility of the transformation of the front of a single photon by a finite dielectric is demonstrated.     

FINITE-DIFFERENCE TIME-DOMAIN ANALYSIS OF UNMAGNETIZED PLASMA PHOTONIC CRYSTALS

The plasma photonic crystal is a periodic array composed of alternating thin unmagnetized (or magnetized) plasmas and dielectric materials (or vacuum). In this paper, the piecewise linear current density recursive convolution finite-difference time-domain method for the simulation of isotropic unmagnetized plasma is applied to model unmagnetized plasma photonic crystal structures. A perfectly matched layer absorbing material is used in these simulations. In time-domain, the electromagnetic propagation process of a Gaussian pulse through an unmagnetized plasma photonic crystal is investigated. In frequency-domain, the reflection and transmission coefficients through unmagnetized plasma photonic crystals are computed and their dependence on plasma frequency, plasma thickness, collision frequency is studied. The results show theoretically that the electromagnetic bandgaps of unmagnetized plasma photonic crystals are tuned by the plasma parameters.