Near field coupling in passive and active terahertz metamaterial devices

A wide variety of optical phenomena rely on the near field manipulation and confinement of electromagnetic field in subwavelength metallic and dielectric resonators with applications ranging from the design of micro and nano scale photonic devices to super lenses and ultrasensitive sensors. In this invited paper, we present a discussion on controlling the metamaterial properties by active and passive manipulation of near field coupling in an array of split ring resonators. We show that near field coupling between the meta-atoms could lead to resonance tuning, mode splitting, and ultrafast switching in passive and active resonators. The near field coupling schemes discussed here demonstrate the application possibilities of such structures towards the design of active switches, amplitude modulators, frequency agile behaviors, and slow light devices, particularly for the terahertz frequency regime, which still suffers from the shortage of practical devices required to bridge the so called 'THz gap.'