Terahertz electromagnetic response of split ring resonators

Abstract

Utilizing terahertz time domain spectroscopy system, we have characterized the electromagnetic response of a planar array of split ring resonators (SRRs) fabricated upon a high resistivity GaAs substrate. We discuss the phenomena of resonant transmission and absorption experimentally, and analyze the factors that affect the frequency of the resonant transmission peak. Free charge in metal rings occurs directional moving with effects of electric and magnetic fields when terahertz wave is incident in split ring (SR). It makes transmission and absorption peaks at certain frequencies by electric and magnetic responses between metal rings. There is another kind of absorption which is made by its structure at natural frequency of SR. We demonstrate, SRR structure has anisotropic property. The directions of split will decide transmission mode of terahertz in samples. Different modes of dipole oscillating are made by changing electric wave vector, and its absorption is also affected. However, natural frequency of SRR is decided by lattice size, independent of transmission mode. Magnetic response occurs when magnetic wave vector has component which is normal to sample surface. It makes phenomenon of absorption more apparently. In addition, decreasing component of which is parallel to sample surface can make transmission peak move to low frequency. Infections to resonance properties of SRR by terahertz electric and magnetic wave vectors are discussed in this letter. It can be a reference for researching terahertz devices.