Terahertz for the Study of Metamaterials
Metamaterials are artificial materials engineered to provide control over electromagnetic waves. They are composed of sub-wavelength metallic resonators mounted periodically on dielectrics.
In metamaterials the unit cells can be manipulated and constructed to resonate at various frequencies obtaining unique electromagnetic responses differently from electromagnetic responses of natural substances that are of a limited range as derived from atoms and molecules in unit cells.
The most popular unit cell is split ring resonator (SRR), which has two interleaved metallic rings with two opposite gaps. When the incident magnetic field is perpendicular to the SRR plane, electric currents are induced along the rings. Simply, each unit cell acts as an LC oscillator and responses to the external magnetic field at the resonance frequencies.
Using Terahertz Time-domain Transmission Spectrum on DSRR
A study undertaken at Yonsei University using TeraView's TPS Spectra 3000 Spectrometer investigated a superlattice structure of planar metamaterial where the orientation of double-split ring resonator (DSRR) is altered in a periodic way, a useful tool for angle-selective enhancement of local fields.
Microscope pictures of (a) reference metamaterial and (b) sample metamaterial superlattice are shown along with (c) polarization angle of E-field. THz transmission spectra of (d) reference metamaterial and (e) and (f) sample metamaterial superlattice are shown for different polarization angles.
The study utilising with time-domain terahertz transmission spectrum, concludes that alternately oriented DSRRs superlattice structure permits angular control of the amount of anti-symmetric current flows among the nearest-neighboring metaparticles. The metamaterial superlattice is also observed to be a useful tool for angle-selective enhancement of local fields in the study of the structure edges of graphene.
Absorption characteristics of silicon microring resonators at terahertz frequencies were demonstrated in a paper published by the University of Glasgow, Zeeko and TeraView Ltd in the Journal of Applied Physics: Terahertz localized surface plasmon resonance of periodic silicon microring arrays.
In a separate paper, Parallel laser microfabrication of large-area asymmetric split ring resonator metamaterials and its structural tuning for terahertz resonance, resonance properties of asymmetric split ring resonator (ASRR), terahertz metamaterials with different gap sizes at one side, are investigated.