ITERATIVE CALCULATION, MANUFACTURE AND INVESTIGATION OF DOE FORMING UNIMODAL COMPLEX DISTRIBUTION

We present results of iterative calculation, manufacture and experimen tal as well as theoretical investigations of a novel diffractive optic al element (DOE) which transforms a Gaussian TEM00 input beam into a u nimodal Gauss-Hermite (1, 0) complex distribution. The iterative calcu lation procedure is based on the application of the method of generali zed projections. The projection operator onto a set of modal functions is implemented through partition of the focal plane into a 'useful' a nd an 'auxiliary' domain. This element is manufactured as a 16 level s urface profile by (variable dose) electron-beam direct-writing into a PMMA resist film, and a subsequent development procedure of the resist . The final element consists of a fused-silica substrate coated with t he structured PMMA film. Both computational and experimental results a re presented and demonstrate a good conformity with each other. The ac hieved results show good prospects of such an approach for the formati on of unimodal distributions. (C) 1998 Elsevier Science Limited. All r ights reserved.