Characterization of 1D diffractive optical elements by phase inversion

We consider the feature dimensions of selected 1D diffractive optical eleme nts (DOE) such that the Fourier transform based Gerchberg-Saxton (GS) itera tive scalar phase retrieval algorithm, as calibrated by the results of vect or coupled-wave theory, may be used for phase reconstruction. We consider e xamples only of continuous surface relief and binary (two level, not multi- level) phase-only DOE. Experimental phase distribution for rectangular and blazed gratings with similar to 5 lambda period agree within experimental l imits with scalar theory, and, for the rectangular grating, were shown to a gree also with the vector theory. Phase distributions are considered for a continuously varying linear blazed grating with 10 lambda periodicity, its sampled binary equivalent with minimum feature sizes of 0.1 lambda and for continuous linear blazed gratings with period varied from similar to 16 lam bda to similar to 2 lambda. The vector calculations show an average linear dependence of the phase on grating period, but the vector curves are displa ced to lower values from the scalar results by an increasing amount as the grating period is reduced. Grating performance is more influenced by the si ze of the grating period than the subwavelength size of the features in a b inary representation. Reasonable equivalence is found in the prediction of correct phase distributions between scalar and vector theory for grating pe riods > similar to 5 lambda.