Readout contrast beyond diffraction limit by a slab of random nanostructures

A simplified Fourier optics approach is applied to study how near-field optical disks retrieve evanescent signals through random nanostructure. The statistical properties of the random nanostructures are used to realize the general behavior of near-field optical disks. The mechanism of its super-resolution capability and an analytical expression of the readout contrast of near-field optical disks with random apertures are derived. The resolution of near-field optical disk is determined by the size of the random nanostructure. © 2007 Optical Society of America.