Tunable ultra-wideband terahertz filter based on three-dimensional arrays of H-shaped plasmonic crystals

A face-to-face system of double-layer three-dimensional arrays of H-shaped plasmonic crystals is proposed, and its transmission and filtering properties are investigated in the terahertz regime. Simulation results show that our design has excellent filtering properties. It has an ultra-wide bandgap and passband with steep band-edges, and the transmittance of the passband and the forbidden band are very close to 1 and 0, respectively. As the distance between the two face-to-face plates increases, the resonance frequency exhibits a gradual blueshift from 0.88 THz to 1.30 THz. Therefore, we can dynamically control the bandwidths of bandgap and passband by adding a piezoelectric ceramic plate between the two crystal plates. Furthermore, the dispersion relations of modes and electric field distributions are presented to analyze the generation mechanisms of bandgaps and to explain the location of bandgaps and the frequency shift phenomenon. Due to the fact that our design can provide many resonant modes, the bandwidth of the bandgaps can be greatly broadened. This paper can serve as a valuable reference for the design of terahertz functional devices and three-dimensional terahertz metamaterials.     

级联参量振荡产生太赫兹辐射的理论研究

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     

纳米硅薄膜/多孔氧化铝复合体系光致发光的温度特性

利用高真空电子束蒸发方法在多孔氧化铝衬底上生长了纳米硅薄膜,经过650℃高温真空退火后,在10～300K温度范围内观测样品的荧光光谱特性,并对样品进行了场扫描电镜(SEM)、傅里叶变换红外吸收(FTIR)光谱、X射线衍射(XRD)谱的分析。PL谱结果表明,随着温度的升高,样品的发光峰位一般发生红移,但在50～80K范围内却出现了反常的蓝移现象;样品的发光强度基本是按逐渐减小趋势变化的。在60～80K之间,发光强度有少许变强。讨论了纳米硅薄膜的光致发光机理,用量子限制-发光中心模型对实验现象进行了解释。