Design of A Subwavelength Focus Lens Based on the Manipulation of Spoof Surface Plasmons

Terahertz imaging is attractive in the nondestructive test, material characterization, security scanning, and medical screening. However, its resolution is limited by the diffraction limit. In this work, a two-dimensional metal pillar array with varying heights is exploited to manipulate the spoof surface plasmons on the metal pillar array. Via adjusting the dimensions of the pillar, the propagation of spoof surface plasmons on the array can be controlled. Based on this principle, a THz lens that can realize subwavelength focusing with a full width at half maximum (FWHM) being 0.166λ is proposed. The lens can be further extended and may be potential in THz subwavelength imaging.