基于人工微结构的大面积高效率近红外吸收器

基于人工微结构超材料的先进理念,设计制备工作波长可调的近红外大面积吸收器.器件制备采用纳米微球化学自组装方法制备顶层金属微结构,该方法可制备大面积样品.实验结果显示,吸收器在近红外波段峰值吸收率超过99%,吸收波长可以通过结构单元几何尺寸调节.理论模拟结果不但与实验测量的数据相一致,而且很好地阐述了器件高效光吸收的物理机理.     

Modulation of Fano resonances by an external magnetic field in semiconductor quantum wells

We have studied the dimensionality dependence of the behavior of Fano resonances in the photoluminescence excitation spectra of GaAs---Al_xGa_1−xAs heterostructures in a magnetic field applied in the Faraday configuration. A striking difference is observed between quasi-two and quasi-three-dimensional systems: while the Fano profiles evolve into Lorentzian lineshapes in two-dimensional systems, Fano resonances emerge from the continuum in three-dimensional-systems with increasing magnetic field.     

A high-performance multi-wavelength optical switch based on multiple Fano resonances in an all-dielectric metastructure

The multi-wavelength optical switch based on an all-dielectric metastructure consisting of four asymmetric semi-circular rings was designed and analyzed in this paper. Four Fano resonance modes, which can be explained by bound states in the continuum(BIC) theory, are excited in our structure with a maximum Q-factor of about 2 450 and a modulation depth close to 100%. By changing the polarization direction of the incident light, the transmission amplitude of Fano resonances can get effectively mo...     

一种新型基于MIM等离子体环形谐振器的可调谐高性能多信道波分解复用器的设计

设计并研究了基于金属-介质-金属等离子体环形谐振器的可调谐高性能多通道波分解复用器。通过环形腔的谐振理论分析,发现通过调节环形腔的半径和填充介质折射率可以很容易地控制波分复用器的信道波长,与有限元法模拟得到的结果吻合得很好。由等离子体波导和多个环形谐振器组成的多信道WDM结构增加了在电信波长的传输率,传输率高达80%,比最近文献中报道的结果高出两倍。所设计的多信道波分解复用器在高集成电路中有重要潜在应用。     

Terahertz phononic crystal in plasmonic nanocavity

Interaction between photons and phonons in cavity optomechanical systems provides a new toolbox for quantum information technologies. A GaAs/AlAs pillar multi-optical mode microcavity optomechanical structure can obtain phonons with ultra-high frequency(～THz). However, the optical field cannot be effectively restricted when the diameter of the GaAs/AlAs pillar microcavity decreases below the diffraction limit of light. Here, we design a system that combines Ag nanocavity with GaAs/AlAs phononic ...     

基于等离激元纳米结构非对称集成的二维材料自驱动光响应增强的研究进展（特邀）

金属-二维材料-金属是最常见的二维材料光探测器件的结构。由于结构简单、易于集成,该类器件受到最广泛的关注和研究。其自驱动光探测的模式具有很低的暗电流,有望成为高性能红外探测的新途径。然而金属-二维材料-金属的自驱动光探测存在两个瓶颈问题:（1）反对称的金属-二维材料结区引起的泛光照射下光响应的抵消;（2）二维材料有限光吸收导致的低响应率。文中介绍了利用等离激元纳米结构的非对称集成引入非对称的光耦合,从而打破泛光照射下二维材料与两端电极接触区域产生的光电流的对称性,实现净的自驱动光响应;同时利用等离激元纳米结构产生的局域强光场提高二维材料光吸收率和光响应率的一系列研究进展。在石墨烯等离激元纳米谐振腔复合结构中,实现两个电极附近的光响应对比度超过100倍,突破了对称光耦合导致的光响应抵消的难题。由于具有将入射光耦合成局域模式的优越能力,等离激元纳米谐振腔比亚波长金属光栅更有效地提高石墨烯响应率一个数量级以上。     

复合鱼鳞型超构材料中光控Fano谐振的设计

为解决传统超构材料存在的结构一旦形成,其谐振特性便无法进行动态可调的问题,本文将鱼鳞型超构材料与光电导材料硅相结合,实现了太赫兹波段Fano电磁响应的动态调控。该复合超构材料由鱼鳞型金属线、硅层以及聚酰亚胺组成。在鱼鳞型结构的金属弧线无、有缝隙两种情况下,研究了电磁波的入射角度和硅的电导率对Fano谐振的影响。当硅的电导率达到1×103S/m时,多频点电磁响应的调制深度都接近1。结果表明,调节缝隙宽度可以成为Fano谐振工作频率调控的有效方式。本文为实现超构材料中Fano谐振的可调谐特性提供了一种可行途径,对实际应用中太赫兹波的主动调控、传感等方面具有重要意义。     

仙农—范诺编码方法的C语言实现

按照概率匹配的方法 ,即概率大的编码短的原则 ,可以在给定信息条件下 ,减少平均编码长度 ,提高编码效率 ,使每个码元所载荷的平均信息量为最大。     

Fano effect in the magnetoabsorption spectra of gallium arsenide

The magnetooptic absorption spectra of high-quality homoepitaxial GaAs layers in a magnetic field B up to 7.5 T at T=1.7 K are investigated. It is shown that the Fano effect is involved in the formation of certain lines of the magnetooptic spectrum. The parameters of the phenomenological Fano function are determined. It is shown that polariton effects of the diamagnetic exciton play a significant role in the investigated processes. Fiz. Tekh. Poluprovodn. 33, 19–24 (January 1999)     

Performance of modified Fano algorithm in AWGN and fading channels

A computationally efficient modified Fano algorithm for decoding of convolutional codes, recently proposed by the authors [1] has been further studied through simulation. Computational efforts and the BER performance of the original Fano and the modified Fano algorithms have been compared for the i) BSC and ii) Rayleigh fading channel with flat fading assumption. For the simulation example, the performance of the modified Fano algorithm was found to be comparable to the Viterbi decoder.     

Dimensional magnetic resonances in nanostructure systems

It is shown that magnetic interaction of closely spaced atoms is an electromagnetic field leads to the formation of dimensional magnetic resonances with small widths and frequencies that differ considerably from the frequency of the magnetic resonance of an isolated atom and depend strongly on the interatomic distance and polarization of the external field. The interactions between two identical atoms and between two different atoms are considered with allowance for spin and orbital quantum transitions. Dimensional magnetic resonances in a diatomic nanostructure system are studied on the basis of a non-perturbation-theory-based solution to a system of equations for the field and atomic variables.     

Low-frequency resonances in hollow metamaterial cylinders

The 2D problem of excitation of a hollow circular metamaterial cylinder by a filament source is analytically and numerically investigated. It is found that, when the relative permittivity and permeability are close to minus unity, high-Q resonances exist in hollow cylinders of an electrically small radius. Near- and far-field patterns are calculated. It is found that, under resonance conditions, a multilobe scattering pattern typical of superdirective antennas is formed. The influence of loss on the resonance characteristics is investigated.     

Negative refraction in 1D plasmonic photonic crystals

The phenomenon of negative refraction of light in 1D photonic crystals with metal layers is studied. It is demonstrated that this phenomenon is due to the excitation of plasmons, which transfer energy in different directions the metal and inside the dielectric layers. The ratio between these two fluxes determines the sign of the group velocity, and therefore, the sign of the refraction angle. It is shown that the sign of refraction is independent of the metal permittivity dispersion and is determined by the permittivity value and by the geometric parameters of an elementary cell only.     

Hybrid-phonon resonances in a quantum channel

Intraband absorption of electromagnetic radiation by electrons in a quantum channel in a transverse quantizing magnetic field is studied. In the calculation, the interaction of conductivity electrons with optical phonons is taken into account. An analytical expression for the coefficient of absorption of high-frequency electromagnetic radiation is derived. It is shown that the absorption spectrum exhibits asymmetric resonance peaks, and the positions of the peaks are determined. The dependence of the absorption coefficient on the magnetic field is studied.     

Energy intensity analysis of modes in hybrid plasmonic waveguide

A hybrid plasmonic waveguide containing silicon core,silver cap and ultra-thin sandwiched SiO2 layer is studied.By analyzing the mode distribution patterns and the curves of mode effective index,we sho...     

基于硅基微环谐振器的Fano共振线型产生和调谐研究进展

Fano共振的线型具有明显不对称特征,在光学通信、调制和传感等领域中极具应用潜力。首先对微环谐振器的各种线型进行了介绍,强调了Fano共振线型的独特优势,其次依据结构分类梳理了国内外基于硅基微环谐振器产生Fano共振的研究现状,然后介绍了基于热光效应的Fano共振调谐的研究进展,最后展望了硅基微环谐振器的Fano共振的发展及应用。     

Undesired resonances in oversized rippled-wall mode converters

A new method to study rippled-wall mode converters based on a generalized investigation of multi-resonance phenomena in periodically perturbated circular oversized waveguides is presented. These resonances cause serious problems in the design of advanced, very high-power millimetre wave mode converters. The concept of a mode diagram helps in the initial design steps to get a global feel for possible resonances at each frequency and waveguide diameter. The optimal conversion path is determined from this mode diagram to avoid unwanted mode resonances. This method is shown applied to a TE_0.1?TE₀₃converter with a waveguide diameter of 27-79mm working at 60GHz. This converter is very close to the worst resonance effect (first-order resonance: |β₀₃? β₀₄.| ≈| β₀₃? β₀₁ |) which destroys totally the desired conversion effect. The second example shown is a TE₀₂?TE₀₁ converter with a waveguide diameter of 44-45 mm working at 28 GHz. In this case the resonance effect is of second order (i.e. | β₀₂? β₀₃|≈2| β₀₁? β₀₂|).