Resonance-order-dependent plasmon-induced transparency in orthogonally arranged nanocavities.

We investigate plasmon-induced transparency (PIT) in a resonator structure consisting of two orthogonally arranged metal-insulator-metal nanocavities. Finite-difference time- domain simulations reveal that when both cavities in this structure resonate at the same frequency, the PIT effect can be used to induce spectral modulation. This spectral modulation depends on the resonance order of the cavity coupled directly to the external field, as it occurs when first-order resonance is exhibited but not with second-order resonance. We confirmed that this behavior is caused by the discrepancies between odd-order and even-order resonances using classical mechanical models analogous to nanocavities. By tuning the resonance frequency and resonance order of the cavities, one can modulate the spectrum of the resonator structure in an order-selective manner. The resonant order-dependent PIT provides insight into the development of metamaterials that function only at specific resonant orders for incident waves of various bands.