Micro diffractive optics is an emerging technology with many applications. The practical applications of diffractive optics technology have driven the need for mathematical models and numerical algorithms. In this talk, recent developments on direct and inverse problems in the mathematical modeling of diffractive optics will be reported. Particular attention will be paid to a variational approach. For the direct problem, the speaker will present a new variational formulation and results on the well-posedness and convergence analysis of the PDE model. Computationally, an interface least-squares finite element method will be discussed. For the inverse problem, recent results on uniqueness, stability, and numerical reconstruction will be presented.