We present and demonstrate a new type of single resonator based planar metamaterial exhibiting electromagnetically induced transparency (EIT)-like transmission behavior. The novel design involves physically coupled split-ring resonator (SRR) and a dipolar ring as opposed to many inductively coupled resonators explored in the past. Both experiments and simulations reveal a dispersive transparency due to coupled resonances and the underlying mechanism. Further, the conductive and inductive coupling scenarios for this structure were compared where conductive coupling was found to coerce the direction of light induced currents and stronger in effect than inductive coupling. Resonance tuning is achieved by moving the bar coupling SRR and the ring. Hence, we show that conductive coupling has potential in tailoring coupled resonances of desired quality factor and fabricating metamaterials for enhanced sensing.
Two layer vertical coupling photonic structures can be directly fabricated on a standard SOI wafer using a combination
of reactive ion etching (RIE) and proton beam irradiation followed by electrochemical etching. The top layer structures
are defined by RIE on the device layer, while the bottom layer structures are defined by proton beam irradiation on the
substrate. Light coupling between the structures in the two layers has been demonstrated via vertical coupling
waveguides. According to simulations, the coupling efficiency mainly depends on the thickness of the two layer
structure and the gap between them. In this process, the thickness of the top layer structures is fixed by the device layer
thickness of the SOI wafer, which is typically 200-300 nm. The gap depends on the thickness of the oxide layer of the
SOI wafer, and it can be shifted due to the natural bending of the top layer structures. The bottom layer structure
thickness can vary due to different energies of proton beam. Furthermore we show the fabrication of tapered bottom
waveguides, which are thin at the coupling region for higher coupling efficiency, and thick at the end for easily coupling
light from an optical fiber or a focused lens.