Effect of fabrication defects on wavefront control characteristics of terahertz dielectric metamaterials

Abstract We clarified the effects of fabrication defects on the wavefront control characteristics of dielectric metamaterials deflecting terahertz waves, and also proposed and demonstrated a design that reduces the effects. Dielectric metamaterials, in which microstructures such as pillars and holes are arranged on a dielectric substrate with a subwavelength period, can efficiently control the wavefronts of terahertz waves. The reported dielectric metamaterial succeeded in deflecting transmitted waves to 46 ∘ at 0.4 THz by periodically arranging through holes of different sizes on a silicon substrate. However, the described metamaterial showed inverse tapering of the holes and notching. It is difficult to eliminate these fabrication defects because deep etching of several hundred micrometers is required to achieve sufficient phase modulation for wavefront control. In this paper, the effects of fabrication defects on terahertz wave control characteristics were investigated, and it was revealed that inverse tapering of the holes decreases and shifts to a higher frequency in the deflection efficiency and that notching also causes them slightly. We proposed and demonstrated a metamaterial design that reduces the effects of fabrication defects to obtain characteristics equivalent to an ideal model without fabrication defects.