The generation of optical beams with multiple, mutually coherent orbital-angular-momentum (OAM) modes using phase gratings is analyzed from the perspective of energy distribution and radial mode composition. We show that phase gratings designed with equally weighted Laguerre-Gauss (LG) modes will generate beams with uneven energy distribution among OAM components. This unwanted outcome cannot be corrected by adjusting the width of the illuminating beam. We propose a way to design phase gratings that will produce a uniform energy distribution among the constituent OAM states after illumination while minimizing the content of high radial modes. This method is based on a generalized definition for the LG modes that take advantage of the freedom to select their radial scales.
Bibliographical noteFunding Information:
Manuscript received December 20, 2017; revised February 21, 2018; accepted February 25, 2018. Date of publication February 28, 2018; date of current version March 23, 2018. This work was supported by the Chilean Science and Technology Commission (CONICYT) under Grant FR-1160887. Corresponding author: Jaime Cisternas (e-mail: firstname.lastname@example.org).
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