Subwavelength focusing by combining negative-refractive photonic crystal and silicon lens

We propose a new and dynamically focusable subwavelength focusing system, consisting of a negatively refracting photonic crystal and a single silicon lens. The system can adjust the focal length in the range of 370 nm to 4610 nm. We set directional light with a wavelength of 1612nm to incident on the whole system. Numerical simulation through RSOFT shows the smallest focus spot with the half-width of 0.116 λ at a distance of 0.44 λ and calculates focusing efficiency of 45%. In addition, a good result is found that the half-width of the spot is less than 1/2 wavelength at a distance of 2.85 λ from the surface of the structure.