A beam shaping method is presented where a diffractive optical element (DOE) is designed by optimizing the complex mode coefficient weights of a set of Gaussian beam modes. This method is compared with the more standard unidirectional approach. Differential evolution is used for the optimization in both the unidirectional and Gaussian beam mode optimization methods. For the particular transforms carried out, the Gaussian beam mode set optimization (GBMSO) approach achieved more optimal solutions. The GBMSO approach is extended to design DOEs that control the amplitude distribution of a beam at multiple planes, rather than at just a single plane (i.e., the far field).