Terahertz metasurface studies based on the near-field spectroscopy

Metasurface, as a kind of metamaterials with only one or two layers of functional structures, has arouses a world-wide research enthusiasm during the past several years. Especially, recent studies on metasurfaces working in the terahertz regime has partly fullfilled the emergent lack for the terahertz devices, which is a long-term bottleneck on the terahertz science and technology. Until now, most terahertz metasurfaces were designed, demonstrated and applied for the far-field utilization. However, in recent years, kinds of near-field terahertz technique have become more and more powerful and convenient to use, which facilities a new aspect of terahertz metasurface research. Here we presented the recent terahertz near-field studies on several metasurface-based terahertz devices, including two anomalous surface wave couplers and a meta-lens array. The near-field method not only gives a new tool for the terahertz metasurface study, but also makes the terahertz surface wave researches possible, which may broadly promote the development of the terahertz device technology.