Experimental verification of sub-wavelength focusing via a holographic metallic screen

In this paper we have experimentally demonstrated the viability of a subwavelength focusing screen, formed by placing slot antennas over a ground plane. In a proof-of-principle experiment using only 3 slots, we have focused the x-directed e-field to a FWHM of 5.2 mm (0.17-wavelength) at an image plane 4.5 mm (0.15-wavelength) from the screen at f = 10 GHz. Our measured results indicate that the screenpsilas focusing quality and the electric field intensity at the focal spot are only minimally affected by conductor losses. We have also verified that resonant coupling enhances the peak field intensity at the focal spot to a level comparable to the incident field. The loss independence and high transmitted peak intensity make our subwavelength focusing screen an attractive option for practical subwavelength focusing in the near-field.