Fabry–Prot (FP) resonators with metallic subwavelength grooves or holes, which have been extensively applied in optical region, have recently attracted increasing interest for terahertz wave generation and manipulation. However, the practices of such resonators in the terahertz region are greatly restricted by the low energy-capacity and by the difficulty of manufacturing high-aspect-ratio grooves/holes. Here we illustrate a kind of terahertz FP resonator formed by a cluster of coupled grooves with low-aspect-ratio, which has much higher energy-capacity, higher quality-factor and is much easier to fabricate than one formed by a single uncoupled-groove. Using free-electron beams to excite an array of such FP resonators, coherent terahertz emission can be achieved, the intensity of which is more than an order of magnitude higher than that from an array of uncoupled-grooves, affording a promising way for high-power and coherent terahertz wave generation.

具有金属亚波长凹槽或孔的Fabry–Prot（FP）谐振器已广泛应用于光学领域，最近引起了人们对太赫兹波产生和操纵的兴趣。然而，太赫兹区域中的这种谐振器的实践受到低能量容量和制造高纵横比凹槽/孔的困难的极大限制。在这里，我们说明了一种由纵横比很低的耦合凹槽簇构成的太赫兹FP谐振器，它比单个非耦合凹槽形成的太赫兹FP谐振器具有更高的能量容量，更高的品质因数并且更容易制造。使用自由电子束激发这种FP谐振器阵列，可以实现相干太赫兹发射，