Abstract
Quasi-continuous metasurfaces are widely used in various optical systems and their subwavelength structures invalidate traditional design methods based on scalar diffraction theory. Here, a novel vector iterative Fourier transform algorithm (IFTA) is proposed to realize the fast design of quasi-continuous metasurface beam splitters with subwavelength structures. Compared with traditional optimization algorithms that either require extensive numerical simulations or lack accuracy, this method has the advantages of accuracy and low computational cost. As proof-of-concept demonstrations, several beam splitters with custom-tailored diffraction patterns and a 7 × 7 beam splitter are numerically demonstrated, among which the maximal diffraction angle reaches 70° and the best uniformity error reaches 0.0195, showing good consistency with the target energy distribution and these results suggest that the proposed vector IFTA may find wide applications in three-dimensional imaging, lidar techniques, machine vision, and so forth.
Highlights
The maximal diffraction angle and uniformity error are two important indicators that determine the performance of the device
Traditional methods based on scalar diffraction theory for designing beam splitters can hardly enable a large diffraction angle and low uniformity error owing to the limitation of paraxial approximation and electromagnetic coupling [20]
Before the whole optimization starts, the period of the beam splitter is determined by the grating equation according to the required diffraction angle and diffraction patterns [29]
Summary
A quasi-continuous metasurface beam splitter divides one laser beam into multiple beams and can be applied in structured light [13,14,15,16], optical interconnects [17], and camera calibration [18,19]. For these applications, the maximal diffraction angle and uniformity error are two important indicators that determine the performance of the device. Traditional methods based on scalar diffraction theory for designing beam splitters can hardly enable a large diffraction angle and low uniformity error owing to the limitation of paraxial approximation and electromagnetic coupling [20]
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