Compact on-chip THz circular polarization detectors with high discrimination based on chiral plasmonic antennas

Abstract

THz circular polarization detection is an important technology in many applications of THz waves. With the ongoing miniaturization of optoelectronic systems, there is an increasing demand for compact on-chip THz circular polarization detectors. Here, we propose what we belive to be a novel device of this kind based on the composite structure of quantum well (QW) infrared detection material sandwiched by a chiral plasmonic antenna array and a metal plane. Due to the circular polarization dependent light coupling discrimination provided by the cavity enhanced chiral antenna and the second polarization selection of the QWs, a circular polarization extinction ratio as high as 25 is achieved, surpassing all reported on-chip THz circular polarization detectors. Due to the field enhancement at the QWs, the absorption for the principle circular polarization is 15 times higher than a standard reference. The absorption peak can be tuned over the range from 6.41 to 6.56 THz, while considerable absorption enhancement and high circular polarization discrimination are preserved even under non-normal incidence. Our proposed device's structure is compatible with the QWIP focal plane array and has far-reaching application prospects opens a new avenue to the development of high-performance compact on-chip THz circular polarization detectors.