一维微等离子体光子晶体的太赫兹带隙特征调控

调控太赫兹波传播是太赫兹技术应用的基础。从麦克斯韦方程组和电子动量守恒方程出发,推导了等离子体的相对介电系数和电导率。在此基础上,从理论和仿真两个层面,论证了一维微等离子体光子晶体(MPPC)用于太赫兹带隙特征调控的可行性,结果表明:在无缺陷的一维MPPC中,当电子数密度低于10~(15) cm~(-3)时,电子数密度的改变对第一太赫兹禁带影响较微弱;当电子数密度从10~(15) cm~(-3)继续升高到10~(16) cm~(-3)时,第一禁带的中心频率向高频偏移110 GHz,第一禁带的宽度增加约200 GHz。气压从50.5 kPa增大到202 kPa,第一禁带的中心频率从0.871THz下降到0.79THz。在含单个缺陷的一维MPPC中,当电子数密度从10~(14) cm~(-3)增加至10~(15) cm~(-3)时,窄通带的中心频率偏移约24 GHz。由此可见,在光子晶体中引入微等离子体后,其能够对太赫兹波传播进行调制。     

Ka波段平板光子晶体波导传输特性测量

为了测量在Ka波段下空气孔型平板光子晶体波导的传输特性,提出采用从金属矩形波导将电磁波耦合进光子晶体波导并测量其传输特性的测试方案。根据两种波导传输模式的场分布,用两段介质尖劈作为电磁波从矩形波导到三角形晶格平板光子晶体波导的模式转换结构,该结构使用电磁场仿真软件找出最优结构尺寸。实验使用聚合物聚醚酰亚胺（PEI）作为介质材料,加工出实际结构,采用AV3629网络适量分析仪测试整个系统的S参数;结果在27~40 GHz之间的传输系数为？7 dB左右,将测试数据与数值结果相比较,并重新设置PEI材料的损耗参数进行仿真,最终,测试结果在损耗角正切为5×10？4的情况下与仿真数据相一致,表明本文提出的模式转换结构有效,平板型光子晶体结构在微波波段的应用打下基础。     

基于USB的主动太赫兹成像电路设计

简要介绍了一套针对双波段主动太赫兹无损检测系统研制的基于USB通信的电路系统.该电路系统可通过控制二维扫描机构实现太赫兹无损检测系统的二维扫描,利用双波段太赫兹探测器接收经目标反射的由双波段太赫兹源辐射的太赫兹信号,并对该信号利用过采样方式实现数据采集,通过USB实现数据的上位机传输,并最终利用频域滤波和小波变换等图像处理技术实现主动太赫兹成像.成像结果表明,电路系统符合实际需求,双波段太赫兹无损检测系统可实现分辨率3 mm的无损检测,能很好地满足泡沫等非极性材料的无损检测的应用需求.     

基于光子晶体结构的微环谐振器的传输特性分析

本文针对基于硅基光子晶体结构的双信道单环谐振器的传输特性进行了系统的模拟研究工作,分析中应用了有限时域有限差分法(FDTD)设计进行微环谐振器的建模和传输特性的分析。建立一种基于三角光子晶体结构的微环谐振器模型,并通过改变结构参数,构建不同的微环谐振器模型结构。同时,利用matlab软件对不同模型结构的微环谐振器仿真结果进行处理分析。其满足谐振条件的光波通过谐振器时,能够进行耦合,仿真得到的谐振器输出端的传输效率达到0.96,与理论分析结果基本相似。本文对理解基于光子晶体结构的微环谐振器的工作机制、传输特性分析以及自主设计有所帮助,并为其实际应用提供了理论分析基础。     

光子晶体光纤的研究进展

在14篇文献的基础上，综述了光子晶体新型介质材料的能带结构、带隙产生、制备方法，对光子晶体光纤的制备技术与应用以及新的实验和理论进展作了重点介绍，对其发展前景进行了展望。     

基于PBG结构微带天线增益的研究

提出了1种具有二维光子晶体带隙结构的微带贴片天线.光子晶体是1种人造的电介质结构在空间上的周期性分布,本文采用的方法是在微带贴片天线介质基片中引入周期性分布的空气孔,并且针对不同的孔径大小对天线的增益特性进行了研究和比较.本文采用模拟仿真软件HFSS对这些结构进行了模拟仿真,仿真结果表明PBG结构能够有效地提高微带天线...     

ESD辐射场与带孔缝金属腔体耦合的数值研究

采用FDTD法研究了ESD电流注入细导线所产生的辐射场在其近场区域与带孔缝金属腔体的耦合问题 ,建立了耦合数值模型。计算分析表明 ,在金属腔体内的孔缝周围区域存在较强的耦合场 ,腔体内被激励起以TE10 1模、TE2 0 1模和TE112 模为主的谐振场 ;对面积相等的方孔、矩形孔和孔阵 ,通过长边与导线垂直的矩形孔和方孔的耦合场比较强 ,而通过长边与导线平行的矩形孔和孔阵的耦合场比较弱     

全息光子晶体LED的制作技术

在发光二极管（LED）表面制作二维光子晶体可以提高其外量子效率。本文提出一种利用激光全息技术将二维光子晶体结构制作于LED表面的新方法。这种二维光子晶体基于光栅衍射原理将限制在LED内的波导光提取出来。初步实验结果显示当在GaN基蓝光LED表面的ITO电流扩展层制作晶格常数为1．2微米、深度约0．2微米的二维六角光子晶体时，LED的发光强度提高了35％。     

太赫兹光谱技术的应用进展

近年来太赫兹（THz）技术快速发展,在安全检测、航空航天、生命科学、化学等领域应用日趋广泛。由于许多炸药及其相关材料在THz波段具有特征吸收,许多非金属、非极性材料对THz波是透明的,且太赫兹波具有低能性,THz光谱技术在安检中具有巨大的应用潜力。本文介绍了太赫兹波的特性和国内外在太赫兹领域的研究进展,详细介绍了太赫兹波在爆炸物、毒品和包装材料检测中的应用,并讨论了在应用中存在的困难和面临的挑战。     

太赫兹电磁波检测复合绝缘子内部缺陷可行性研究

复合绝缘子的电气性能和机械性能是输电线路安全运行的重要影响因素。研究使用太赫兹电磁波对复合绝缘子内部缺陷进行无损检测的可行性。该方法将激光器产生的太赫兹电磁波通过光路传输到绝缘子内部。利用脉冲电磁波在不同电磁介质内的传播特性,通过分析反射波的时域特征,判断复合绝缘子样品内部的情况。通过对平面形状样品和实际绝缘子样品进行试验,对比有无缺陷情况下的检测波形,证明了太赫兹方法是检测复合绝缘子内部缺陷的有效方法。     

Light Emission From Silicon in Photonic Crystal Nanocavity

We have introduced a photonic crystal into a single-crystal silicon slab in order to manipulate the light emission. When the lattice constant of a defect-free photonic crystal matches the wavelength of light in the medium, the light emitted from the silicon is resonantly extracted at the photonic band edge within the escape light cone. When the lattice constant is larger than the wavelength, Brillouin zone folding of the photonic band also allows the light to be extracted; we achieved an intensity that was enhanced by a factor of ~ 20 due to the diffraction of internal light into the light cone. We have also created a point defect in photonic crystals with smaller lattice constants that functions as a nanocavity and strongly interacts with the silicon emitter. Four cavity modes were observed, with different Q -factors and emission patterns. The mode orders were assigned using the resonant wavelengths and polarizations. The observed emission at room temperature was enhanced by a factor of ~ 30 in comparison to that of an unprocessed area of silicon-on-insulator. Our study demonstrates that employing a photonic crystal nanocavity in silicon can greatly improve the light extraction efficiency, the characteristics of the radiation pattern, and the internal quantum efficiency.     

Analysis of polarization plane rotation characteristic in 2D photonic crystal waveguide with chiral medium by condensed node spatial network

Using the photonic band gap in photonic crystals, the fundamental waveguide structures for the light wavelength range have been developed. Based on the fine structure of these many functional devices have been proposed by analytical or numerical simulation methods and the experiments of trial manufacture. In this paper, the treatment of chiral dielectric in the Condensed Node Spatial Network for the vector potential is explained, and we show the polarization plane rotation property in air‐hole and pillar type photonic crystal waveguide structures with the chiral medium substrate. Then, we show the fundamental advantage of the air‐hole type photonic crystal waveguide structure in application to a mode converter. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(1): 7–14, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20098     

Ferroelectric Based Photonic Crystal Cavity by Liquid Crystal Infiltration

A novel type of two-dimensional photonic crystal is investigated for it optical properties as a core-shell-type ferroelectric nanorod infiltrated with nematic liquid crystals. Using the plane wave expansion method and finite-difference time-domain method, the photonic crystal structure, which is composed of a photonic crystal in a core-shell-type ferroelectric nanorod, is designed for the square lattice and the hexagonal lattice. It has been used 5CB as a photonic crystal core, and LiNbO₃ as a ferroelectric material. The photonic crystal with a core-shell-type LiNbO₃ nanorod infiltrated with nematic liquid crystals is compared with the photonic crystal with solid LiNbO₃ rods and the photonic crystal with hollow LiNbO₃ rods.     

Analysis of finite-size coated electromagnetic bandgap structure by an efficient scattering matrix method

This paper presents an efficient simulation algorithm-Scattering matrix method for investigation of the coated finite two-dimensional electromagnetic bandgap (EBG) structures. The method is derived to be capable to simulate the band properties of the coated cylinder photonic crystal with wave discontinuities. Numbers of photonic crystals with waveguide discontinuities are examined. The transmission characteristics of the EBG embedded with metal, dielectric, and various coated cylinders are analyzed. The results show that the tuned bandgap properties are able to provide an additional possibility to develop a novel device.     

Self-collimation in planar photonic crystals

We analyze, in three dimensions, the dispersion properties of dielectric slabs perforated with two-dimensional photonic crystals (PCs) of square symmetry. The band diagrams are calculated for all k-vectors in the first Brillouin zone, and not only along the characteristic high-symmetry directions. We have analyzed the equal-frequency contours of the first two bands, and we found that the square lattice planar photonic crystal is a good candidate for the self-collimation of light beams. We map out the group velocities for the second band of a square lattice planar PC and show that the group velocity is the highest in the region of maximum self-collimation. Such a self-collimated beam is predicted to show beating patterns due to the specific shape of the equal-frequency contours. A geometrical transformation maps the region of the first and second photonic bands where self-collimation takes place one onto the other and gives additional insights on the structural similarities of self-collimation in those two bands.     

Analysis of band gap of non-bravais lattice photonic crystal fiber

This article designs a novel type of non-bravais lattice photonic crystal fiber. To form the nesting complexperiod with positive and negative refractive index materials respectively, a cylinder with the same radius and negative refractive index is introduced into the center of each lattice unit cell in the traditional square lattice air-holes photonic crystal fiber. The photonic band-gap of the photonic crystal fiber is calculated numerically by the plane wave expansion method. The result shows that compared with the traditional square photonic band-gap fiber (PBGF), when R/Λ is 0.35, the refractive index of the substrate, airhole, and medium-column are 1.30, 1.0, and −1:0, respectively. This new PBGF can transmit signal by the photonic band-gap effect. When the lattice constant Λ varies from 1:5 μm to 3:0 μm, the range of the wavelength ranges from 880 nm to 2300 nm. __________ Translated from Optoelectronic Technology, 2007, 27(4): 257–260 [译自: 光电子技术]     

Planar photonic crystal coupled cavity waveguides

We present absolute transmission measurements of coupled cavity waveguides defined within planar photonic crystals. We investigate a range of cavity types and also vary the spacing between cavities. Modal analysis of the individual cavities reveals the symmetries that determine the coupling between adjacent cavities. Enhanced transmission is demonstrated by modifying the photonic crystal lattice. We highlight the need for correct impedance matching at the waveguide input in order to improve the transmission.     

Enhancement of light extraction from two-dimensional photoniccrystal slab structures

Efficient light extraction from various two-dimensional photonic crystal slab structures is studied. By using the finite-difference time-domain method, effects of finite air-hole depth, and the cladding refractive index on the light extraction efficiency are investigated. The largest extraction efficiency is obtained in the photonic crystal slab with entirely drilled air hole patterns and large index contrast with the bottom cladding. Using InGaAsP quantum wells emitting at 1.5 μm large enhancement of photoluminescence is observed from the slab structures with air-hole patterns fully transferred through the active medium and the bottom cladding. The photoluminescence enhancement relative to the as-grown wafer is ~8 in the oxide-supported slab and ~13 in the free-standing slab. The large light extraction enhancement results from the coupling to leaky modes above the light line of a band structure. In addition, the extraction behaviors of a triangular lattice and a square lattice are compared, and it is shown that their distinctive extraction characteristics well reflect the features of each band structure     

Photonic crystals and microdisk cavities based on GaInAsP-InPsystem

This paper presents a preliminary guide to realize microcavity semiconductor lasers exhibiting spontaneous emission control effects. It includes: 1) theoretical consideration on the effects; 2) processing techniques for semiconductor microcavities; and 3) some demonstrations of photonic crystal and microdisk cavity. It was shown that, even with a spectral broadening of electron transition, thresholdless lasing operation and alternation of spontaneous emission rate are expected in a cavity satisfying the single mode condition that only one mode is allowed in the transition spectrum. An ideal three-dimensional (3-D) photonic crystal has the potentiality for realizing this condition. In two-dimensional (2-D) crystals and microdisk cavities, thresholdless operation is also expected, but the alternation of spontaneous emission rate may be negligible due to the insufficient optical confinement. In the experiment, some processing techniques for GaInAsP-InP system were investigated and methane-based reactive ion beam etching was selected because of the smooth sidewalls and adaptability to arbitrary structures. A GaInAsP-InP 2-D photonic crystal constructed by submicron columns was fabricated using this method. Owing to the slow surface recombination of this material, a polarized photoluminescence and peculiar transmission spectra were observed at room temperature (RT), which can be explained by a photonic band calculation. However, some technical improvement is necessary for clear demonstration of photonic bandgap, which is minimally required for device applications. In contrast to this, a GaInAsP-InP microdisk cavity of 2 μm in diameter, which corresponds to the cavity volume 2.5 times the single-mode condition, has achieved RT lasing with threshold current as low as 0.2 mA. Further reduction of diameter and realization of continuous-wave (CW) operation will provide a significant regime for the observation of spontaneous emission control effects