In earlier chapters, the design of DOEs and the simulation of their far-field
diffraction patterns using Fraunhofer diffraction formula were presented. However, to characterize a DOE, it is necessary to analyze phase and intensity profiles at different propagation distances. For instance, the binary axicon or circular grating generates a ring-like pattern in its far field, and it generates a Bessel-like beam closer to the element. With its large focal length, the Bessellike
beam, is used for many applications. Hence, it is necessary to simulate and understand the field variations at several planes of interest. In this chapter, a MATLAB simulation of diffraction patterns in the Fresnel regime is presented. The analysis and simulation presented here are not suitable for planes very close to the DOE.
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