Hyperbolic Metamaterials for Collimation and Subwavelength Focusing

Collimation and focusing are generally more common in optics field. We demonstrate hyperbolic metamaterials (HMMs) with very flat isofrequency surfaces in wavevector space for tunneling of electromagnetic (EM) energy, which lead to collimation and subwavelength focusing at microwave frequencies. The HMM as a transmission device has been realized by employing two-dimensional metamaterial transmission lines. In HMM operates in canalization regime, the EM waves with different incident angles were refracted in a direction. The HMMs can couple evanescent waves with high wave vectors into propagating modes, and as a result, they provide subwavelength focusing. Focusing of with the narrowest full width half maximum (FWHMs) of about 1/32 of the wavelength at 0.95GHz is confirmed. The numerical simulation and the experimental measurement show good agreement.