Terahertz metalenses for evanescent wave focusing and super-resolution imaging

Abstract

Super-resolution focusing in the metamaterials for both the propagating and evanescent wave emerging from free space is demonstrated based on the gradientindex (GRIN) metalenses. The theoretical investigation reveals that the evanescent wave in free space can be transformed into propagating wave in the metamaterial due to the specific dispersion of the metamaterial. So spatial Fourier transform (FT) with broad input angular spectrum are achieved when the metamaterials are designed with GRIN. Furthermore, the application of super-resolution imaging based on the spatial FT is also presented.

Metalens Antennas in Microwave, Terahertz and Optical Domain Applications

“…Figure 16 shows the structure that the metasurface unit cell is a silicon cube sitting on top of a Si substrate, and a SiO2 thin layer is inserted in between. The unit cell size is 46.9 μm × 46.9 μm and the width of the cube W is 10.7 μm, the length L is 38.7 μm, and the thickness t is 80 μm [14][15][16] (Figures 17-20). A scanning near-field THz microscope (SNTM) setup in figure 15 is built to characterize the focusing effect of the metalens, which is made of THz photoconductive generation and probe detection.…”