Terahertz beam focusing through designed oblique metal-slit array.

ABSTRACT

Manipulation of propagating beams is essential in applications, and the potentially arising phenomena offer attractive optical components. However, the design of optical components using only naturally occurring materials has approached physical limits, and artificial materials such as metamaterials and metasurfaces are a way forward to open the door to sophisticated optical components. This paper shows manipulation of terahertz beams through designed oblique metal-slit arrays where a common metal-slit array does not perform as a lens. The oblique metal-slit array has a refractive index determined as a function of a steep angle. The lens consists of multiple metal plates with a designed oblique angle, and a convex output structure produces a focusing effect. We also suggest that the Brewster phenomenon in the lens can simply enhance the electric field intensity at the focal point. The Brewster condition of the lens is correlated with a jagged edged face on the input side with an appropriate metal-slit spacing and thickness. The phenomenon would be applicable to numerous promising components and applications such as gain-enhancement optical components and perfect impedance-matching polarizers.