Periodical subwavelength light focusing by proximity projection grating structure

The authors developed a technique of generating periodical subwavelength light focusing array. In the technique, a proximity projection grating structure (PPGS) is employed. The size of focal spot obtained is dependent on the refractive index of film material used in the PPGS. When the film with the refractive index greater than 4 is used, focal spots with size of can be obtained. Additionally, the subwavelength light focusing will appear periodically along the propagation direction, which leads to the light focusing in both near field and far field. Both simulations and experiments verify the developed technique. The periodical subwavelegnth light focusing array has the potential in super resolution imaging applications.