Effective Fresnel number and focal shifts for focused cylindrical spherical aberrated beams |
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Authors: | Lifen Shi Jixiong Pu |
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Affiliation: | aDepartment of Electronic Science and Technology, Huaqiao University, Quanzhou, Fujian, 362021 China |
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Abstract: | We define the effective Fresnel number of a focused cylindrical spherical aberrated beam. Based on the effective Fresnel number, a simple analytical expression for evaluating the relative focal shift is presented. It is shown that the relative focal shift is determined by the effective Fresnel number, which is dependent on the spherical aberration and Fresnel number of the focused system. To illustrate the approach, a comparison between the results obtained by this new method and the numerical integral calculation is made. The results indicate that the relative focal shift can be simply and exactly evaluated using this new method. A special case is discussed, in which the effective Fresnel number turns out to be a pure imaginary number, and the corresponding relative focal shift is positive. |
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Keywords: | Focal shift Effective Fresnel number Spherical aberration |
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