A new method for determining phase in optical diffraction patterns

Abstract

A method is described for the measurement of the relative phases of beams of laser light diffracted from a centrosymmetrical two-dimensional optical diffraction grating. The method relies upon the observation of interference effects when adjacent orders of diffraction yield overlapping beams of parallel light. The Fresnel diffraction pattern recorded is crossed by interference fringes whose positions and intensity distributions are governed by the phases and amplitudes of the diffracted beams. Computer simulation of the diffraction pattern indicates the possibility of phase recovery from patterns given by centrosymmetric diffraction gratings when two, three or four beams overlap, and suggests that the method may be extended to diffraction patterns from non-centrosymmetric gratings also. The potential of the method as an analogue for phase determination in crystallographic problems is indicated.