Spatial Phase and Amplitude Structuring of Beams Using a Combination of   Multiple Orthogonal Spatial Functions with Complex Coefficients
  Analogous to time signals that can be composed of multiple frequency functions, we use uniquely structured orthogonal spatial modes to create different beam shapes. We tailor the spatial structure by judiciously choosing a weighted combination of multiple modal states within an orthogonal basis set, and we can tunably create beam phase and intensity "shapes" that are not otherwise readily achievable. As an example shape, we use a series of orbital-angular-momentum (OAM) functions with adjustable complex weights to create a reconfigurable spatial region of higher localized power as compared to traditional beam combining. We simulate a structured beam created by coherently combining several orthogonal OAM beams with different complex weights, and we achieve a >10X localized power density enhancement with 19 beams. Additionally, we can create unique shapes by passing a single beam through a specially designed phase and intensity mask that contains the combination of multiple OAM functions each with complex weights. Using this approach, we experimentally demonstrate a ~2.5X localized power density increase when utilizing 9 functions. 
Guodong Xie, Cong Liu, Long Li, Yongxiong Ren, Zhe Zhao, Yan Yan,   Nisar Ahmed, Zhe Wang, Asher J. Willner, Changjing Bao, ...
physics.optics