The Smith–Purcell radiation (SPR) is a promising way for developing compact and high power terahertz sources with broad application prospects. Yet, the conventional SPR is largely restricted by its low efficiency and incoherency. Here we illustrate an enhanced coherent SPR from a compound array of deep-narrow-rectangular-grooves (DNRGs). We show, by detailed theoretical analysis and simulations, that each DNRG is an effective resonant cavity with low radiating Q-factor and a cluster of closely adjacent DNRGs can get enhanced coherent emission. More notably, by setting clusters of DNRGs with gradient shapes to be periodically arranged in an array, we can change the conventional incoherent SPR to be a coherent emission with a series of specified frequencies at specified directions, namely, the radiation is discretized. The total radiation efficiency can be increased by more than an order of magnitude. Thus, it affords an efficient way for high power multicolor terahertz generation...

中文翻译：

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Smith-Purcell辐射的光谱离散化，可实现高效的多色太赫兹发射

Smith-Purcell辐射（SPR）是开发具有广阔应用前景的紧凑型和高功率太赫兹源的有前途的方法。然而，常规的SPR很大程度上受到其低效率和不连贯性的限制。在这里，我们从深窄矩形凹槽（DNRG）的复合阵列中说明了增强的相干SPR。通过详细的理论分析和仿真，我们表明，每个DNRG是一个有效的谐振腔，具有低辐射Q因子，并且紧密相邻的DNRG簇可以增强相干发射。更值得注意的是，通过将具有渐变形状的DNRG的簇设置为周期性排列在阵列中，我们可以将常规的非相干SPR更改为在指定方向上具有一系列指定频率的相干发射，即辐射被离散化。总辐射效率可以提高一个数量级以上。因此，它为高功率多色太赫兹生成提供了一种有效的方法。