One important aspect of the proposed research is to design and demonstrate the use of metasurfaces as smart reflectors to enhance the capabilities of networks operating above 100 GHz. This effort will involve facing several challenges. One key challenge is in the design of the metasurface. Even in the limit of these two-dimensional tiled structures, there is an enormous parameter space that can be explored, and no well-established route to optimizing or even exploring this space of possibilities. We have solved one of the important aspects of this problem, by demonstrating a new method for sample preparation. In most previous work involving THz metasurfaces, samples have been prepared using photolithography. This is, of course, a very well-known procedure, very well established in every clean room. But, it is not fast, or efficient. By contrast, our approach involves simple patterning and printing using a hot-stamping method, which requires nothing more sophisticated than a computer, a conventional laser printer, and alaminator. These common office tools can be employed to create arbitrary micro-scalemetal patterns on paper, which can be designed in Powerpoint and then printed andlaminated in about 10 minutes.
We have demonstrated that metasurfaces consisting of a tiled array of split ring resonators can be fabricated in this fashion, with optical properties that rival those of the photolithographically-defined equivalent structures. The technique works well for structures with resonant responses up to about 500 GHz – at higher frequencies, the needed printing resolution is smaller than can be easily achieved using a conventional 1200 dpi printer. This breakthrough will allow us to test many different types of passive metasurfaces, including both homogeneous and in homogeneous patterns, since, for the first time ever, the sample fabrication now takes less time than is required to make the THz spectroscopy measurement. This result has been published in Optics Express in 2021.
Publications:
Guerboukha, Hichem and Amarasinghe, Yasith and Shrestha, Rabi and Pizzuto, Angela and Mittleman, Daniel M. (2021). High-volume rapid prototyping technique for terahertz metallic metasurfaces. Optics Express. 29 (9) Article No.13806.