A new THz technology: artificial dielectrics

摘要

In recent years, the THz field has gained considerable interest in the scientific community due to a multitude of potential applications, ranging from spectroscopy to communications. However, there is a lack of fundamental device components that are needed to propel the field from mere scientific curiosities to real-world applications. And, the quest for high performance, energy efficient, and low cost device architectures that could manipulate THz radiation is an on-going endeavor. Here, we review recent work on how to fabricate several fundamental THz devices by revitalizing an age old, little known, and unconventional material-design technology called artificial dielectrics. These are man-made media that mimic the properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. Using artificial dielectrics, we demonstrate a lens that can focus THz radiation, a polarizing-beamsplitter that can split an arbitrarily polarized beam into two linearly polarized orthogonal components, a quarter-waveplate that can change a linearly polarized beam into a circularly polarized one, and an isolator that can minimize harmful back-reflections. These artificial-dielectric devices exhibit remarkable performance characteristics, exceeding what has been reported in the literature, in some cases by several orders of magnitude. Indeed, our device specifications rival those of similar functional devices commercially available for optical wavelengths. Furthermore, the inherent simplicity of the device geometry makes these devices inexpensive to fabricate.