Subdiffraction focusing of total electric fields of terahertz wave

Terahertz lens is an essential component in terahertz application. We propose a focusing of total electric fields planar lens based on super-oscillation. This planar lens is designed for a wavelength (λ) of 118.8μm with a radius of 160λ, a focal length of 210 λ and a numerical aperture of 0.606. Our experiment demonstrates a subdiffraction and subwavelength focusing of total electric fields. The full width at half-maximum of the focal spot is 0.67 λ, which is smaller than the diffraction limit of 0.825λ. The results shows that it has powerful application for terahertz imaging, especially in the fields of biomedical science.