Abstract-Eigenmode hybridization enables lattice-induced transparency in symmetric terahertz metasurfaces for slow light applications

Joshua A. Burrow, Riad Yahiaoui, Andrew Sarangan, Jay Mathews, Imad Agha, and Thomas A. Searles

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-11-2705

Traditional lattice-induced transparency demonstrations are activated by varying the meta-atom lattice constant such that the plasmonic and lattice modes interfere. Here we report on the observation of enhanced coupling between two eigenmodes (first- and second-order) by varying the lattice parameter in a symmetric split ring resonator design. The higher-order quasi-dark mode blueshifts, introducing strong coupling with the fundamental bright mode for periods above 345 μm. Numerical simulations are verified experimentally and supplemented with a two-oscillator model showing good agreement. Furthermore, larger positive group delay values are achieved in the vicinity of the transparency window with minimal absorption, indicating a strong potential for slow light applications.

© 2019 Optical Society of America

Abstract-Influence of symmetry breaking on Fano-like resonances in high Figure of Merit planar terahertz metafilms

Joshua A. Burrow, Riad Yahiaoui, Wesley Sims, Zizwe A. Chase, Viet Tran, Andrew Sarangan, Jay Mathews, Willie S. Rockward, Imad Agha, Thomas A. Searles

https://arxiv.org/abs/1812.02063

It is well established that nearly all high-quality (Q) Fano-like resonances in terahertz (THz) metasurfaces broaden as asymmetry increases, resulting in a decline of Q-factor and an increase in the resonance intensity. Therefore, in order to determine the optimal design for applications in THz sensing, a Figure of Merit (FoM) is required. Previous studies have identified the asymmetry regimes at which the peak FoM occurs for various, specific unit cell geometries. However to date, there is no systematic comparison of the resulting FoMs for common and novel geometries. Here, a THz planar metafilm featuring split ring resonators with four distributed capacitive gaps is investigated to compare three unique methods of implementing asymmetry: (1) adjacent L-bracket translation, (2) capacitive gap translation and (3) increasing gap width. The results obtained find that by translating two gaps and increasing the bottom gap width of the unit cell, the high-Q Fano-like resonances are 6× higher than the FoM for the fundamental dipole mode. This work further informs the design process for THz metasurfaces and as such will help to define their applications in photonics and sensing.

Abstract-Electromagnetically induced transparency control in terahertz metasurfaces based on bright-bright mode coupling

Riad Yahiaoui, Joshua A. Burrow, Sirak M. Mekonen, Andrew Sarangan, Jay Mathews, Imad Agha, Thomas A. Searles

http://arxiv-export-lb.library.cornell.edu/abs/1712.08733

We demonstrate a classical analogue of electromagnetically induced transparency (EIT) in a highly flexible planar terahertz metamaterial (MM) comprised of three-gap split ring resonators. The keys to achieve EIT in this system are the frequency detuning and hybridization processes between two bright modes coexisting in the same unit cell as opposed to bright-dark modes. We present experimental verification of two-bright mode coupling for a terahertz EIT-MM in the context of numerical results and theoretical analysis based on a coupled Lorentz oscillator model. In addition, a hybrid variation of the EIT-MM is proposed and implemented numerically in order to dynamically tune the EIT window by incorporating photosensitive silicon pads in the split gap region of the resonators. As a result, this hybrid MM enables the potential active optical control of a transition from the on-state (EIT mode) to the off-state (dipole mode).

Abstract-Polarization-dependent electromagnetic responses of ultrathin and highly flexible asymmetric terahertz metasurfaces

Joshua A. Burrow, Riad Yahiaoui, Andrew Sarangan, Imad Agha, Jay Mathews, and Thomas A. Searles

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-26-32540

We report the polarization-dependent electromagnetic response from a series of novel terahertz (THz) metasurfaces where asymmetry is introduced through the displacement of two adjacent metallic arms separated by a distance δ. For all polarization states, the symmetric metasurface exhibits a low quality (Q) factor fundamental dipole mode. By breaking the symmetry, we experimentally observe a secondary dipole-like mode with a Q factor nearly 9× higher than the fundamental resonance. As δ increases, the fundamental dipole mode f1redshifts and the secondary mode f2 blueshifts creating a highly transmissive spectral window. Polarization-dependent measurements reveal a full suppression of f2 for all asymmetries at θ ≥ 60°. Furthermore, at δ ≥ 60 μm, we observe a polarization selective electromagnetic induced transparency (EIT) for the fundamental mode. This work paves the way for applications in filtering, sensing and slow-light devices common to other high Q factor THz metasurfaces with EIT-like response.

© 2017 Optical Society of America under the terms of the OSA Open Access Publishing 

Abstract-Polarization-dependent electromagnetic responses of ultrathin and highly flexible asymmetric terahertz metasurfaces

Joshua A. Burrow, Riad Yahiaoui, Andrew Sarangan, Imad Agha, Jay Mathews, Thomas A. Searles

(Submitted on 18 Oct 2017)

https://arxiv.org/abs/1710.06714

We report the polarization-dependent electromagnetic response from a series of novel terahertz (THz) metasurfaces where asymmetry is introduced through the displacement of two adjacent metallic arms separated by a distance δ. For all polarization states, the symmetric metasurface exhibits a low quality (Q) factor fundamental dipole mode. By breaking the symmetry, we experimentally observe a secondary dipole-like mode with a Q factor nearly 9× higher than the fundamental resonance. As δ increases, the fundamental dipole mode f1 redshifts and the secondary mode f2 blueshifts creating a highly transmissive spectral window. Polarization-dependent measurements reveal a full suppression of f2 for all asymmetries at θ≥60∘. Furthermore, at δ≥60 μm, we observe a polarization selective electromagnetic induced transparency (EIT) for the fundamental mode. This work paves the way for applications in filtering, sensing and slow-light devices common to other high Q factor THz metasurfaces with EIT-like response.