Three-dimensional energy-controllable focal spot array with extended depth of focus created by pure phase modulation

To produce a three-dimensional (3D) energy-controllable focal spot array with an extended depth of focus (EDOF), we propose a pure phase modulation that combines a two-dimensional (2D) pure phase sinusoidal grating (2D PSG) and a light sword optical element (LSOE). The intensity distribution in the 3D focal field is achieved by both simulation and experiment, exhibiting high energy controllability and EDOF. Additionally, the position of the maximum intensity value of any focusing spot exhibits a rotation characteristic, further indicating that the EDOF can be continuously extended. The transverse spacing between adjacent foci, the shape of the focusing spot, and the intensity distribution are achieved in comparison between simulations and experiments, showing good conformity in two situations of f₁/f=10% and 20%. Our proposed method paves a new way to produce the 3D energy-controllable focal spot array with EDOF, laying a solid foundation for its application in various fields, such as 3D photonic crystal structures, 3D luminescence, and 3D optical sensing.