Laser applications that demand a high quality with long coherence length are limited by the Gaussian profile of the fundamental TEM00 mode. Many of these applications require a uniform irradiance profile with a flat phase-front. In holography, both phase and intensity are critical to the process. Near-field beam shaping optics, also called beam transformers, re-map an input Gaussian profile to a top-hat profile. The top-hat profile is created at some working distance away from the shaping element where a corrector element has traditionally been placed in order to flatten the phase of the top-hat profile and allow it to propagate as a nominally collimated beam. This paper will discuss the theory to support the use of a diffractive optical element in holography and other applications where the phase is important. Two different geometric beam shapes will be explored, round and square profiles.
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