Focusing of light beyond the diffraction limit of half the wavelength.

The diffraction limit sets the smallest achievable linewidth at half the wavelength. With a subwavelength plasmonic lens allowing one to reduce the diffraction via an asymmetry and to generate and squeeze the wave functions, an incident light is focused by the aperture to a single line with its width smaller than the limited value in the intermediate zone. The focused fields are capable of propagating in free space. This light focusing process, besides being of academic interest, is expected to open up a wide range of application possibilities.