We investigate the electromagnetic response of asymmetric broadside coupledsplit ring resonators (ABC-SRRs) as a function of the relative in-planedisplacement between the two component SRRs. The asymmetry is defined as thedifference in the capacitive gap widths (\Delta g) between the two resonatorscomprising a coupled unit. We characterize the response of ABC-SRRs bothnumerically and experimentally via terahertz time-domain spectroscopy. As withsymmetric BC-SRRs (\Delta g=0 \mu m), a large redshift in the LC resonance isobserved with increasing displacement, resulting from changes in the capacitiveand inductive coupling. However, for ABC-SRRs, in-plane shifting between thetwo resonators by more than 0.375Lo (Lo=SRR sidelength) results in a transitionto a response with two resonant modes, associated with decoupling in theABC-SRRs. For increasing \Delta g, the decoupling transition begins at the samerelative shift (0.375Lo), though with an increase in the oscillator strength ofthe new mode. This strongly contrasts with symmetric BC-SRRs which present onlyone resonance for shifts up to 0.75Lo. Since all BC-SRRs are effectivelyasymmetric when placed on a substrate, an understanding of ABC-SRR behavior isessential for a complete understanding of BC-SRR based metamaterials.
展开▼
