Folded slot resonator array with efficient terahertz transmission

We investigated transmission characteristics of folded slot resonators on a free-standing thin stainless steel film in terahertz frequency. The transmission at the resonance determined by the length of the slot was roughly proportional to the cosine function of the angle between directions of the slot and the polarization of incident light. Generally, the transmission at the resonance in the folded slot resonators was higher than that of a straight slot. Especially, the transmission efficiency at the 60° angle in the folded slot was three times higher than that in the straight slot. This is caused by strong oscillations of the accumulated charges inside the internal area formed by two arms of the folded slot. This finding demonstrates a new method for designing compact structures based on the folded geometry and for realizing THz devices.