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报道了一种基于频率可调谐准高斯太赫兹波束的透射成像系统.研究表明,在这种成像系统中太赫兹波束具有良好的空间分布特性,其波束质量因子M2x=1.15,M2z=1.25,波束传输特性和聚焦特性良好.实验结果反映出成像系统的空间分辨能力与典型太赫兹波长(250μm)相接近.在太赫兹波输出1.0—2.5THz范围内,成像系统信噪比大于1000dB;在1.8THz处,信噪比
关键词:
太赫兹波
太赫兹成像
太赫兹探测 相似文献
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基于受激电磁耦子散射原理,采用已报道的利用非线性光学参量振荡方法产生可调谐太赫兹波的实验条件作为理论分析的实验模型,以GaAs,GaP, InP,ZnTe晶体为代表,计算分析了在闪锌矿晶体中参量振荡产生太赫兹波的吸收、增益特性,对输出THz波的调谐特性给出了详尽分析.分析太赫兹波高效耦合输出的腔型结构,并与掺氧化镁铌酸锂晶体组成的太赫兹波参量振荡器做对比.
关键词:
太赫兹波
太赫兹波参量振荡
电磁耦子
闪锌矿晶体 相似文献
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针对光学参量振荡产生太赫兹波转换效率低的缺点, 提出了级联参量振荡产生太赫兹波的新机理以提高转换效率. 以周期极化铌酸锂晶体为例, 对级联参量振荡产生太赫兹波的原理和过程进行了理论研究. 分析了抽运光波长、周期极化铌酸锂晶体极化周期和工作温度对产生一阶、二阶闲频光频率的影响. 推导了三波共线相互作用条件下太赫兹波的增益特性和吸收特性. 计算结果表明, 通过级联参量振荡可以有效提高太赫兹波的转换效率, 并可以得到宽调谐的太赫兹波输出. 基于分析结果, 设计了周期极化铌酸锂晶体级联参量振荡产生高效率、宽调谐、窄线宽、连续太赫兹波的实验.
关键词:
太赫兹波
太赫兹波参量振荡
级联参量振荡 相似文献
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基于简单紧束缚方法理论,利用一维碳纳米管的量子化周期边界条件得到了碳纳米管的电子能级结构关系.并结合已报道的碳纳米管中电子与声子相互作用的实验结果,得到了碳纳米管能够辐射太赫兹波的结论.通过数值结果验证了碳纳米管在外场作用下能够产生太赫兹波,并对数值计算结果中太赫兹波的振荡现象给予合理的解释.其结果为进行碳纳米管产生太赫兹辐射的实验研究提供深入的理论基础.
关键词:
太赫兹波
碳纳米管 相似文献
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提出了一种基于掺金硅的全光学宽带太赫兹波幅度调制器, 研究了金(Au)点阵掺杂后硅(Si)体内的少数载流子寿命及其太赫兹波调制特性. 实验结果表明, 掺杂的Au原子为Si中的光生电子- 空穴对提供了有效复合中心, 使其少数载流子寿命由原来十几微秒降低至110 ns左右. 利用波长915 nm 调制激光作为抽运光源, 在340 GHz载波的动态调制测试中获得4.3 MHz的调制速率和21%的调制深度, 使Si基调制器的调制速率提高了两个数量级. 该全光太赫兹调制器可工作在整个太赫兹频段内, 具有极化不敏感特性, 因而在太赫兹波高速和宽带调控方面具有重要的应用价值, 也是构建光控型Si 基太赫兹功能器件的重要基础. 相似文献
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通过对磁场控制下的二维磁光子晶体太赫兹波偏振传输特性的研究,利用铁氧体磁光材料的磁导率随外磁场改变而变化的特点,设计了具有可控起偏、偏振分束和可调谐波片功能的光子晶体太赫兹偏振控制器件.利用平面波展开法和严格耦合波分析分别计算了光子晶体带隙位置和透过率随外磁场强度变化的关系,用时域有限差分法计算了场分布和相位.结果表明,该结构可以实现高偏振消光比的偏振起偏器和分束器,以及在1 THz附近-π-π相位范围的连续可调谐波片.
关键词:
太赫兹
光子晶体
铁氧体
偏振控制 相似文献
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高性能的太赫兹器件在控制太赫兹波方面起到重要的作用,因此寻求一种简单有效的太赫兹器件加工方案非常必要。本文以太赫兹波导和太赫兹滤波器为例,分别选用Kagome型光子晶体结构的波导和一维光子晶体结构的滤波器,运用商用的3D打印机加工样品,并采用透射式太赫兹时域光谱系统对样品的参数进行测量。实验结果表明:加工的波导在0.2~1.0 THz范围内传输损耗平均值约为0.02 cm~(-1),最小值可达到0.002 cm~(-1),且可运用机械拼接的方式将多个波导进行简单的连接从而获得更长的波导而不引起严重的损耗;滤波器的透射谱在0.1~0.5 THz之间有两个明显高损耗带;这两组实验结果均与理论预计非常接近。本文运用太赫兹波导和滤波器的实例证实了3D打印技术加工太赫兹器件的可行性,将会成为获取性能可控、价格低廉的太赫兹器件的有效途径。 相似文献
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We numerically demonstrate terahertz multichannel filters with independently tunable defect modes based on fractal photonic crystals. Single defect and multiple defects models are proposed to fabricate the multichannel terahertz filters. The facts that the wave functions of the defect states do not overlap and their bases are orthogonal lead to the independency among the defect modes. The simulated results theoretically provide the principle for fabricating independently tunable multichannel terahertz filters by utilizing one-dimensional photonic crystals with defects. 相似文献
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太赫兹技术在最近30年来得到快速发展, 并在医学、生物、农业、材料、安检、通信、天文等领域得到广泛应用. 从太赫兹源的频谱特性可以分为窄带(单频)太赫兹源和宽带太赫兹源. 从频谱技术方面来说, 相干的宽带和窄带太赫兹谱是一种互补性关系, 具有各自的技术特点和应用范围. 宽带太赫兹谱可以用于快速获取较宽频谱范围的分子振转谱, 实现混合特征谱的快速检测或成像. 窄带太赫兹源具有很好的光谱灵敏度和分辨率, 适用于太赫兹抽运-探测、分子振转能级谱精细结构分辨 以及太赫兹远程探测和成像. 因此研制具有可调谐的高峰值功率的窄带太赫兹源是适用于探测和识别分子振转能级指纹谱的应用需求, 而差频技术是获得高功率和宽调谐窄带太赫兹源最重要的技术之一. 为了突出该技术的最新进展, 本综述引证论文仅仅限于近5 年来基于差频技术产生太赫兹波的研究进展, 分为光学激光差频源和量子级联激光器差频源两大部分. 对于光学激光差频源, 分别对目前文献报道的各种双波长差频源和太赫兹产生用的非线性晶体进行分类介绍, 并给出所采用的技术和实验结果; 对于量子级联激光器差频源, 分别介绍了量子级联激光器中的差频产生技术和波长调谐技术的最新进展. 量子级联激光器差频太赫兹源是目前实现量子级联激光器在太赫兹波段室温运转的惟一技术, 是实现小型化、窄带宽调谐和室温运转太赫兹源的新发展领域, 值得关注. 相似文献
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Kaisar Khan Khaled Mnaymneh Hazem Awad Imad Hasan Trevor Hall 《Applied Physics A: Materials Science & Processing》2014,117(2):629-634
Metamaterials that provide negative refraction can be implemented in photonic crystals (PhCs) through careful design of the devices. Theoretically, we demonstrate that the dispersion can be altered to achieve negative refraction. This can be done through engineering the geometry of the device as well as selecting appropriate materials. The PhC also demonstrates slow light that facilitate sensing chemicals or biological agents. Using metallic materials such as gold nano-particle enables PhCs to guide optical waves in desired pathways. Also using magnetic materials such as highly doped n-GaAs, we can tune the band gap by changing magnetic field. The simulated results are consistent with some of the previously reported experimental results and give us guidance for future experiments. 相似文献
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Doping Defects in Two-Dimensional Holographic Photonic Crystals Using a Continuous-Wave Visible Laser 下载免费PDF全文
It is demonstrated that defects of any shape or size can be doped in holographic photonic crystals using a cw visible laser and spherical/cylindrical lens. Defects with different sizes at any depth in the material can be obtained by controlling the position of the foca/point of the lens and exposure value. We facilitate the implementation of sub-wavelength arbitrary point or line defects in large-size 2D holographic photonic crystals. 相似文献
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We propose that the photonic band structure (PBS) of semiconductor-based photonic crystals (PCs) can be made tunable if the free-carrier density is sufficiently high. In this case, the dielectric constant of the semiconductor, modeled as varepsilon(omega) = varepsilon(0)(1-omega(2)(p)/omega(2)), depends on the temperature T and on the impurity concentration N through the plasma frequency omega(p). Then the PBS is strongly T and N dependent; it is even possible to obliterate a photonic band gap. This is shown by calculating the 2D PBS for PCs that incorporate either intrinsic InSb or extrinsic Ge. 相似文献
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Silvia Gentilini Mauro Missori Neda Ghofraniha Claudio Conti 《Annalen der Physik》2020,532(8):2000005
Multiple scattering of electromagnetic (EM) waves arises in disordered media with a refractive index varying on the scale of the wavelength. The diffusion approximation is a powerful tool to treat multiple scattering as a photon random walk, neglecting resonant phenomena. However, as the light intensity varies on a scale much smaller than the transport mean free path, resonances may occur in media formed by finite-size scatterers and break the diffusion approximation. The energy and phase velocity are very useful tools to reveal the onset of the resonant transport regime. In this paper the study of the propagation of terahertz (THz) waves through 3D random media by employing terahertz time-domain spectroscopy (THz-TDS) is addressed. Specifically, measurements of the electric field transmitted by samples of different thicknesses made of 1 mm diameter silica spheres dispersed in a paraffin matrix at different filling fractions are reported. This investigation has provided an accurate measurement of the EM field phase and, hence, information on the radiation propagation velocity that has enabled the first observation of a photonic glass at the THz range. 相似文献
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Optical trirefringence in photonic crystal waveguides 总被引:5,自引:0,他引:5
Netti MC Harris A Baumberg JJ Whittaker DM Charlton MB Zoorob ME Parker GJ 《Physical review letters》2001,86(8):1526-1529
We demonstrate that 2D photonic crystals can possess optical trirefringence in which there are six field orientations for which linear incident light is not perturbed on reflection or transmission. Such a property is rigorously forbidden in homogeneous nonmagnetic dielectrics which can possess only optical birefringence. We experimentally demonstrate this phenomena in silicon-based mesostructures formed from photonic crystal waveguides embedded in a Fabry-Perot cavity. Multirefringence is controlled by the presence of submicron dielectric patterning and is well explained by an exact scattering matrix theory. 相似文献
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Renlong Zhou Xuewen Wang Yongyi Gao Lingxi Wu Xiaoshuang Chen 《Physics letters. A》2008,372(31):5224-5228
Doped semiconductors are intrinsically homogeneous media. However, by applying an external magnetic field that has a spatially periodic variation, doped semiconductors can behave extrinsically like conventional photonic crystals. It has shown this possibility theoretically by calculating the dispersion relation, transmittance spectra, and the field distribution of a doped semiconductor under an external, spatially periodic magnetic field. The energy distribution for frequencies located in conduct band and value band are also clearly shown, which convinces the extrinsic photonic band structure characteristic. 相似文献