Tunable group delay in a doubly resonant metasurface composed of two dissimilar split-ring resonators

TL;DR

This paper presents a method to continuously control electromagnetic wave group delay using a doubly resonant metasurface with split-ring resonators, enabling tunable delay with high transmittance in the terahertz range.

Contribution

The authors introduce a novel approach to tune group delay via resonance linewidth manipulation in a doubly resonant metasurface, differing from previous EIT-like metamaterials.

Findings

Group delay can be varied from 0 to 20 times the wave period.

Double resonance lines are observed at oblique incidence.

High transmittance is maintained at small group delays.

Abstract

We develop a method to control the group delay of electromagnetic waves continuously using a doubly resonant metasurface. The method is based on the dependences of i) the group velocity in a medium featuring two resonance lines on the resonance linewidths and ii) the resonance linewidth of a metasurface composed of split-ring resonators on an incidence angle of electromagnetic wave. To verify this method for group-delay control, we design a terahertz metasurface composed of two split-ring resonators with different resonance frequencies and numerically analyze the transmission characteristic of the metasurface. Double resonance lines are observed for oblique incidence and the resonance transmission dips become deeper and broader with increasing the incidence angle. The group delay at around the center frequency of the double resonance lines is found to vary in the range about from 0s to 20 times the period of the incident wave with the incidence angle. In contrast with a previously reported method for variable control of group delay using electromagnetically-induced-transparency-like metamaterials, a high transmittance is achieved for a small group delay condition.