title: Impact of Substrate and Bright Resonances on Group Velocity in Metamaterial without Dark Resonator.
abstract: Manipulating the speed of light has never been more exciting since electromagnetic induced transparency and its classical analogs led to slow light. Here, we report the manipulation of light group velocity in a terahertz metamaterial without needing a dark resonator, but utilizing instead two concentric split-ring bright resonators (meta-atoms) exhibiting a bright Fano resonance in close vicinity of a bright Lorentzian resonance to create a narrowband transmittance. Unlike earlier reports, the bright Fano resonance does not stem from an asymmetry of meta-atoms or an interaction between them. Additionally, we develop a method to determine the metamaterial "effective thickness", which quantifies the influence of the substrate on the metamaterial response and has remained challenging to estimate so far. By doing so, very good agreement between simulated and measured group delays and velocities is accomplished. The proposed structure and method will be useful in designing optical buffers, delay lines, and ultra-sensitive sensors.
authors.affiliation: Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Mohammad Parvinnezhad
authors.initials: MP
authors.lastname: Hokmabadi
authors.affiliation: Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Ju-Hyung
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Elmer
authors.initials: E
authors.lastname: Rivera
authors.affiliation: Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kung
authors.affiliation: Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Seongsin M
authors.initials: SM
authors.lastname: Kim