Optical storage read-out of nonlinear disks

The resolution in optical scanning microscopy is limited by the numerical aperture N.A. of the objective and the wavelength of the light lambda, so that the modulation transfer is zero beyond the spatial frequency of 2 N.A./lambda. However, when an optical property of the object changes under the influence of the scanning spot, resolution beyond this classical cutoff frequency is possible. In optical disk systems the object can easily be provided with nonlinear optical properties enabling superresolution.