Abstract
The growth of terahertz technology has opened up the strong potential of various attractive applications
in the terahertz waveband. However, conventional optical elements such as collimated lenses are too
large for the wavelength, and terahertz devices demand compact and thin optical elements for industrial
applications. We propose and design an ultrathin gradient lens with unprecedented high refractive
indices and extremely low refl ection controlled by paired metal cut wires in the 0.3-THz band. We used
a unit model with periodic boundary walls and designed a refractive index neff = 7.06 + j0.330, refl ection
power of 1.0%, and transmission power of 82.0% for the center of the lens. We also designed a refractive
index of neff = 3.55 + j0.0582, reflection power of 15.2%, and transmission power of 81.9% for the
periphery. A full model analysis also verifi es a focusing effect at 4.69 mm (4.69λ 0) from a lens. The
proposed ultrathin gradient lens with high refractive indices and extremely low refl ection will provide
valuable solutions for a wide range of applications.
