基于狄拉克半金属光栅中表面等离子体波的史密斯-珀塞尔相干多频太赫兹辐射

Coherent Multi-frequency Terahertz Radiation Generated from Surface Plasmon Polaritons in Dirac Semimetal Gratings Based on Smith-Purcell Effect

本文提出一种产生相干多频太赫兹辐射的物理机制,即利用电子注激发狄拉克半金属光栅加载介质基底结构中表面等离子体波并通过史密斯-珀塞尔效应和切伦科夫效应转化为辐射场。电子注可以同时激发起两种完全不同的表面等离子体波模式,分别是光栅缝隙内的腔体表面等离子体波模式和光栅表面的常规表面等离子体波模式,它们具有完全不同的激发条件和辐射特性,本文对其中的物理机制进行了详细分析。腔体表面等离子体波模式的色散决定于光栅材料和结构,调节光栅结构和电子注参数能够大范围调节辐射频率。两种表面等离子体波模式对辐射场均有极大的增强。因此,本文提出了一种产生相干、可调、高功率密度、覆盖整个波段的太赫兹辐射的物理机制。

In this paper,a physical mechanism for generating coherent multi-frequency terahertz radiation is proposed,that is,the surface plasmon polaritons(SPPs)in a Dirac semimetal grating with dielectric loading excited by an electron beam can be transformed into radiation through Smith-Purcell Effect and Cherenkov Effect.The electron beam can simultaneously excite two completely different kinds of SPPs modes,namely the cavity SPPs mode in the grating slits and the conventional SPPs mode on the grating surface.The two modes have totally different excitation conditions and radiation characteristics.The physics mechanism is analyzed in detail.The dispersion of the cavity SPPs mode depends on the grating material and structure,thus the radiation frequency can be widely tuned by adjusting the parameters of grating and electron beam.Both SPPs modes greatly enhance the radiation field.The proposed physical mechanism can be used to generate coherent,tunable,high powered radiation covering the whole terahertz band.