Plasmon-induced transparency-like behavior at terahertz region via dipole oscillation detuning in a hybrid planar metamaterial

We investigate a plasmon-induced transparency (PIT)-like behavior at terahertz (THz) region induced by resonance detuning in a hybrid planar metamaterial (MM). Each unit cell of the MM contains two types of dipole oscillation resonators: a cut-wire and a couple of U-shaped resonators in mirror symmetry. The hybridization of above resonators splits the single resonance mode into two side modes in THz transmission spectrum. The side modes are found to induce negative group delays of incident THz wave-packet. The distribution of surface currents and electric energy reveals that the near-field coupling between cut-wire and U-shape resonators results in inductive-capacitive (LC) resonance, which dominates the low frequency side mode, while the high frequency side mode attribute to the triple dipole oscillations. The reduction of the length of cut-wire give rise to a dipole resonance detuning, which enhances the LC resonance via near-field coupling, while attenuates the constructive inference of triple dipole oscillators. The retrieved complex dielectric functions indicate the evolution of LC resonance and triple dipole oscillations. By controlling the dipole resonance detuning appropriately, a man-made transparent tip can be created in between the two side modes. However, such a transparent tip is unable to induce negative group delay. Aforementioned PIT-like behavior can support the design of hybrid planar MMs in application of two-band notch filters or multi-channel buffer in the THz-region. (C) 2010 Optical Society of America