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Nonuniform quantization for diffractive optical elements design

Recently, the applications of diffractive optical element (DOE) for commerce and research have become more and more popular. DOE itself has a lot of advantages like small volume, low weight, ease of reproduce and low cost. A DOE actually can be considered as a wavefront modulator, and its performance can also be described as a complex amplitude transmittance. In the past, we usually design a DOE by quantizing the phase of DOE from Gerchberg-Saxton algorithm or other methods with equal etching-depth and etching-width because of the ease of process. In this paper, we present a novel approach for design DOE. We change the element's etching-depth and etching-width nonuniformly. The reason why we strike out this approach is that one who can control the timing within the etching process can make any depth and width after all. Therefore, we have more components of etching-depth and etching-width that can be produced to reach the better diffractive efficiency on output diffraction plane than the conventional etching method. In terms of our proposed method, the conventional method of DOE design will become a special case of our new approach. According to the minimum etching-depth, we try all possible combinations to find a set of DOEs phases that have better diffractive efficiency than the conventional method can achieve. The DOE design with the proposed method has higher efficiency on output diffraction plane than those achieved by the conventional method.