Abstract-Terahertz lensing effect in high-temperature superconductors

Amirparsa Zivari, Mohammad Reza Tavakol, Amin Khavasi, Behzad Rejaei, 

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-36-5-1241

We show that high-temperature superconductors can be used to build a terahertz superlens. These materials exhibit hyperbolic behavior at frequencies between their two plasma frequencies corresponding to electric fields parallel and perpendicular to their c-axis. Due to the large component of permittivity perpendicular to the c-axis, the resolution of the proposed lens is much below the diffraction limit (

𝜆/1000$\lambda /1000$). In this paper we demonstrate this lensing phenomenon with a simple slab of a high-temperature superconductor.

© 2019 Optical Society of America

Abstract-Terahertz spectrum splitting by a graphene-covered array of rectangular grooves

 Mohammad Reza Tavakol, Amirhossein Saba, Amir Jafargholi, and Amin Khavasi

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-23-4808

We propose a bidirectional terahertz (THz) spectrum splitter using a practically simple metamaterial structure consisting of rectangular grooves covered by graphene. Thanks to the graphene optoelectronic tunability and by adjusting the grooves width, this structure provides nearly 2𝜋$\mathrm{}$phase shift. At the same time, the reflection efficiency is acceptable throughout the phase shifts. We design each of the meta-atoms using a circuit model, and then we synthesize the final supercell based on the generalized Snell’s law so that the structure reflects different frequency waves to totally different directions. The full-wave simulations demonstrate the beam splitting with a remarkable efficiency of around 80%.

© 2017 Optical Society of America