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1.
提出了一种变态光子带隙结构,研究了由这种结构构成的周期慢波系统的Cherenkov辐射源的特性. 利用高频仿真软件以及三维粒子模拟软件对变态及常态光子带隙慢波系统中类TM01模的色散特性及注-波互作用物理过程进行了模拟研究. 结果表明,在变态光子带隙慢波系统中,类TM01模纵向场分量沿角向分布均匀性得到明显改善,能有效抑制非对称模式,提高输出频谱纯度及注-波互作用效率.
关键词:
Cherenkov辐射源
变态光子带隙结构
慢波系统
三维粒子模拟 相似文献
2.
设计了一种能在C波段和X波段实现稳定双频输出的带有非对称谐振反射腔的单电子束同轴相对论返波振荡器。采用耦合阻抗跃变型慢波结构,使用粒子PIC模拟软件进行了粒子模拟研究。模拟结果显示:轴向电场在系统中的分布得到改进,电子束的能散得到改善。在电子束电压511 kV,电流8.95 kA,引导磁场0.73 T的条件下,双频器件实现了8.09 GHz和9.91 GHz的双波段频率稳定输出,平均功率为1.0 GW,波束互作用效率为21.9%, 效率高于空心双波段返波管及其他双波段器件。器件辐射功率的拍频为1.82 GHz,拍波更为明显和稳定。模拟研究中同时发现, 随着慢波结构之间漂移段的变化,双频频率都呈现一种准周期的变化。 相似文献
3.
《中国物理 B》2015,(6)
In this paper,the basic equations of beam-wave interaction for designing the 220 GHz folded waveguide(FW)backward wave oscillator(BWO) are described.On the whole,these equations are mainly classified into small signal model(SSM),large signal model(LSM),and simplified small signal model(SSSM).Using these linear and nonlinear one-dimensional(1D) models,the oscillation characteristics of the FW BWO of a given configuration of slow wave structure(SWS) can be calculated by numerical iteration algorithm,which is more time efficient than three-dimensional(3D)particle-in-cell(PIC) simulation.The SSSM expressed by analytical formulas is innovatively derived for determining the initial values of the FW SWS conveniently.The dispersion characteristics of the FW are obtained by equivalent circuit analysis.The space charge effect,the end reflection effect,the lossy wall effect,and the relativistic effect are all considered in our models to offer more accurate results.The design process of the FW BWO tube with output power of watt scale in a frequency range between 215 GHz and 225 GHz based on these 1D models is demonstrated.The 3D PIC method is adopted to verify the theoretical design results,which shows that they are in good agreement with each other. 相似文献
4.
通过增加外磁场来调控等离子体光子晶体的光子带隙结构,采用时域有限差分算法分析了由本征层为磁化等离子体层和其他电介质材料层交替堆叠而成的磁化等离子体光子晶体的光子带隙结构,数值模拟中采用完全匹配层吸收边界条件以防止边界的反射。由于外磁场的法拉第磁光效应,使等离子体的介电常数随着外磁场的变化而改变。数值结果表明,等离子体光子晶体的带隙特性在一定的频率范围相应地得到调节,实现了频率低于等离子体频率的电磁波也能在等离子体中传播。 相似文献
5.
通过增加外磁场来调控等离子体光子晶体的光子带隙结构,采用时域有限差分算法分析了由本征层为磁化等离子体层和其他电介质材料层交替堆叠而成的磁化等离子体光子晶体的光子带隙结构,数值模拟中采用完全匹配层吸收边界条件以防止边界的反射。由于外磁场的法拉第磁光效应,使等离子体的介电常数随着外磁场的变化而改变。数值结果表明,等离子体光子晶体的带隙特性在一定的频率范围相应地得到调节,实现了频率低于等离子体频率的电磁波也能在等离子体中传播。 相似文献
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提出了一种新型的非对称性散射体的二维六角晶格光子晶体结构–-太极形介质柱光子晶体. 利用平面波展开法从理论研究这种光子晶体结构的能带特性以及结构参数对完全禁带的影响. 研究表明:散射体对称性的打破, TE模和TM模能带宽度和数目都会有所增加, 有益于获得更宽的完全禁带以及更多条完全禁带.通过参数优化, 发现在ε = 17, R=0.38 μm, r=0.36R, θ = 0° 时, 获得最大完全带隙宽度0.0541(ωa/2πc); 在ε = 16, R=0.44, r=0.2R, θ = 0°时, 光子晶体完全带隙数目最多达到8条.
关键词:
光子晶体
禁带
平面波展开 相似文献
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9.
利用2维半全电磁PIC程序进行数值模拟,设计了一种C波段磁绝缘线振荡器。该振荡器在阴极电子发射起点加圆环,控制此处电子束的发射密度,来减少电子能量的损耗,改善束-波互作用;逐渐加大慢波结构的后两个叶片的内半径,增大微波群速度,便于谐振腔中的能量输出,提高微波输出效率;采用两个扼流片有效地阻止了微波功率向二极管区泄漏,相应减小了器件的尺寸。当外加电压为430 kV、束流46 kA时,饱和后输出微波平均功率2 GW,频率3.51 GHz,功率转换效率10%。 相似文献
10.
Photonic amorphous diamond structure with a 3D photonic band gap 总被引:1,自引:0,他引:1
We report that a full three-dimensional (3D) photonic band gap (PBG) is formed in a photonic amorphous structure in spite of complete lack of lattice periodicity. It is numerically shown that the structure "photonic amorphous diamond" possesses a sizable 3D PBG (18% of the center frequency for Si-air dielectric contrast) and that it can confine light at a defect as strongly as conventional photonic crystals can. These findings present important new insight into the origin of 3D PBG formation and open new possibilities in developing 3D PBG materials. 相似文献
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提出了一种新型的具有光子晶体带隙(PBG)结构的返波振荡器(BWO),利用PBG禁带对BWO工作及输出微波模式进行调制,抑制低次模式,工作在高次模式。通过数值模拟给出了介质柱PBG结构的能带图、禁带限制模式电场分布和周期慢波结构的色散关系曲线,选择晶格常数为0.31 cm,介质柱半径为0.12 cm,介电常数为4.0的三角格子PBG结构可以实现在Ka波段的单一类TM03模式工作,在36~40 GHz的频率范围内,器件可以工作在返波状态,周期长度为0.4 cm。 相似文献
13.
Excitation of microwave by an annular electron beam in a plasma-filled dielectric lined waveguide 总被引:1,自引:0,他引:1
Jianqiang Wu Caidong Xiong Shenggang Liu 《International Journal of Infrared and Millimeter Waves》1995,16(9):1573-1581
An axial relativistic electron beam passing through a slow wave structure is unstable to an electromagnetic perturbation whose phase velocity equals the velocity of the beam. This phenomenon of Cherenkov emission is the basis of all traveling wave tubes. In this paper an excitation of Cherenkov radiation by a thin annular relativistic electron beam in a plasma-filled dielectric-lined waveguide is analysed by use of the self-consistent linear theory. The effect of the thin annular electron beam on the beam-wave interaction is completely described by a jump condition. The dispersion equation and the simultaneous condition of the beam-wave interaction are derived. Finally, the growth rate of the wave is obtained, and the effect of the background plasma density and the electron beam radius on the growth rate of the wave are presented.This work is supported by National Natural Science Foundation of China. 相似文献
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Oleg L. Berman Vladimir S. Boyko Roman Ya. Kezerashvili Anton A. Kolesnikov Yurii E. Lozovik 《Physics letters. A》2018,382(31):2075-2080
Two-dimensional graphene-based photonic crystal (GPC) formed by a periodic array of the homogeneous dielectric cylinders etched in the alternating graphene and dielectric layers and its inverse counterpart are considered. The transmittance of the photonic crystal is obtained. The waveguide due to the localization of the electromagnetic wave on the lattice defect that breaks the translational symmetry of the GPC of two different topologies is studied. The different topologies of GPC are characterized by different photonic band structures with different widths of photonic band gaps (PBG) and provide different frequencies for the localized electromagnetic wave due to the defect. The frequencies of the localized mode for both type of the GPC, located inside the lowest PBG, are in the range of THz or tens of THz depending on the topology of the GPC. It is shown that the photonic band gap always can be tuned by changing the chemical potential of graphene to provide formation of the localized photonic mode due to the defect. The technological advantages of the GPC, as well as the opportunity to tune the PBG and the frequency of the localized electromagnetic wave in the terahertz region of spectrum for the GPC are discussed. 相似文献
16.
对速调型相对论返波管慢波结构色散特性及束波相互作用进行了理论研究。色散特性研究表明:器件工作模式为TM01模,近点,耦合阻抗较高。色散特性预测的工作频率与粒子模拟结果非常接近。慢波结构峰值增长率相对较小,这与电子束与慢波结构相距较大有关,因而器件从起振到饱和的时间较长。在束波相互作用理论中,全面考虑了电子束与慢波结构前向波基波、反向波-1次空间谐波及空间电荷场相互作用、谐振反射器对电子束进行的束流调制和能量调制作用,以及调制腔和提取腔处引入的耦合阻抗及轴向波数突变。稳态和非稳态计算结果均获得了超过40%的束波转换效率。 相似文献
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18.
C. Deng J. W. Haus A. Sarangan A. Mahfoud C. Sibilia M. Scalora A. Zheltikov 《Laser Physics》2006,16(6):927-947
Enhanced second-harmonic generation (SHG) conversion efficiency was theoretically predicted in waveguide geometry with coupling to a one-dimensional grating photonic band gap (PBG). We report a series of experiments using samples made with lithium niobate. A waveguide was fabricated near the surface by applying the proton-exchange technique. The characteristics of waveguide modes were determined by several techniques: prism coupling, diffraction, and Cherenkov radiation. The WKB method was used to analyze the results. Ultraviolet laser lithography was applied to make PBG gratings on the sample. We further investigated Cherenkov second-harmonic generation (CSHG), i.e., SHG radiated into the substrate, under the condition of a band-edge PBG resonance in the waveguides. The SHG inside planar waveguides was also experimentally investigated. We fabricated waveguides with multiple pump modes and found that the second mode was more efficient in enhancing the second harmonic signal. This result is explained by our model. Several samples were investigated in detail; the highest conversion efficiency of CSHG with a PBG was enhanced around 50 times above the CSHG signal without a PBG. A numerical model was constructed with parameters calculated from our sample characterization data to interpret the experimental results. 相似文献
19.
X. Ma 《Applied physics. B, Lasers and optics》2006,84(1-2):339-341
Monodispersed silica microspheres of 270 nm are synthesized by a colloidal solution method. Larger scale perfect three-dimensional
photonic crystals (PCs) are rapidly prepared using the evaporation of acetone to self-assemble the microspheres on quartz
substrates by vertical deposition methods. We find that the pseudo-photonic band gap (PBG) of the PC structure changes with
increasing annealing temperature; it drastically shifts from 450 nm for as-grown crystals to 409 nm for annealing at 800 °C.
CdS photonic crystals are formed by infiltrating CdS nanocrystals of 6 nm into the SiO2 PC structure. The transmission and spontaneous emission characteristics of CdS PCs have been investigated. The clear dip
in the spontaneous emission spectrum relates to the photonic band gap of CdS PCs, indicating that the spontaneous emission
is inhibited in the region of the PBG. The emission band of CdS PCs becomes narrower and sharper than that of CdS nanocrystals;
this demonstrates that the emission band and intensity of the luminescent devices will be tuned by controlling the position
of the PBG.
PACS 42.70.Qs; 42.25.Bs; 78.20.-e; 78.55.Et 相似文献
20.
We introduce the concept of a hybrid 2D-3D photonic band gap (PBG) heterostructure which enables both complete control of spontaneous emission of light from atoms and planar light-wave propagation in engineered wavelength-scale microcircuits. Using three-dimensional (3D) light localization, this heterostructure enables flow of light without diffraction through micron-scale air waveguide networks. Achieved by intercalating two-dimensional photonic crystal layers containing engineered defects into a 3D PBG material, this provides a general and versatile solution to the problem of "leaky modes" and diffractive losses in integrated optics. 相似文献