Nonlinear optical lithography with ultra-high sub-Rayleigh resolution

A nonlinear optical, interferometric method for improving the resolution of a lithographic system by an arbitrarily large factor with high visibility is described. The technique is implemented experimentally for both twofold and three-fold enhancement of the resolution with respect to the traditional Rayleigh limit. In these experiments, an N-photon-absorption recording medium is simulated by Nth harmonic generation followed by a CCD camera. This technique does not exploit quantum features of light; this fact suggests that the improved resolution achieved through use of "quantum lithography" results primarily from the nonlinear response of the recording medium and not from quantum features of the light field.