Observation of Broadband Electrically Tunable THz Metamaterials Polarization Conversion

Abstract

Terahertz (THz) spectral region remains a scientifically rich but technologically underdeveloped research area. Since many molecules possess THz spectral fingerprints (ranging from 0.1THz up to 10 THz), and a large variety of non-conductive materials are transparent to THz radiation. THz radiation promises various potential applications. Nonetheless, there exists a shortage of natural materials capable of interacting with THz radiation from which useful THz detectors, emitters, switches, and other devices may be manufactured. Metamaterials, artificially designable structures that render desired optical properties at a given wavelength, could be alternative candidates to design THz devices. They are made by assembling sub-wavelength unit cells called meta-atoms. Metamaterials are well-known for their interesting electromagnetic characteristics. They exhibit extraordinary and unusual responses such as negative refractive index, subwavelength imaging, and invisibility cloak. Polarization conversion devices play a paramount role in the field of photonics because of their ability to manipulate the polarization state of electromagnetic (EM) waves. Such devices have paved the way to significant advancements in prominent technological fields such as communication, imaging, and remote sensing. Recent researches confirm that polarization conversion of the EM waves in the THz frequency regime can be achieved using metamaterials (MM). MMs are artificial materials forged by repeated arrays of sub-wavelength sized meta-atoms. With appropriate designing of these meta-atoms, they can be engineered to manipulate various aspects of the EM wave interacting with them, especially its polarization state.