Dynamical Electric and Magnetic Metamaterial Response at Terahertz Frequencies

TLDR

The study demonstrates, for the first time, dynamical control of the electrical response of split‑ring resonators via photoexcitation of free carriers in the substrate. Terahertz time‑domain spectroscopy was used to characterize the electromagnetic response of a planar array of split‑ring resonators fabricated on a high‑resistivity GaAs substrate. Measured magnetic and electric resonances agree with theory, the SRRs exhibit a negative electric response for two polarizations, a carrier density of ~4×10¹⁶ cm⁻³ can short the SRR gap to suppress the electric resonance—showing terahertz switch capability—and the results suggest similar behavior across a wide frequency range.

Abstract

Utilizing terahertz time domain spectroscopy, we have characterized the electromagnetic response of a planar array of split ring resonators (SRRs) fabricated upon a high resistivity GaAs substrate. The measured frequency dependent magnetic and electric resonances are in excellent agreement with theory and simulation. For two polarizations, the SRRs yield a negative electric response (epsilon < 0). We demonstrate, for the first time, dynamical control of the electrical response of the SRRs through photoexcitation of free carriers in the substrate. An excited carrier density of approximately 4 x 10(16) cm(-3) is sufficient to short the gap of the SRRs, thereby turning off the electric resonance, demonstrating the potential of such structures as terahertz switches. Because of the universality of metamaterial response over many decades of frequency, these results have implications for other regions of the electromagnetic spectrum.