Modulation of high-quality internal multifoci based on modified three-dimensional Fourier transform

We report an efficient method to generate arbitrary three-dimensional (3D) parallel multifoci inside a material. Taking into account the numerical aperture of the objective lens and the refractive index of the material, the Ewald cap was modified with a longer radius, then the whole 3D intensity distribution inside the material could be calculated using only a single Fourier transform (FT). By introducing the adaptive weight coefficient, the uniformity of the 3D multi -foci improves from 81.3% to 98.9%. By adjusting the axial resolution of the Ewald cap, the uniformity of the axial mul-tifoci improves from 85.9% to 99.7%. In the experiment, we have realized one-dimensional (1D), 2D, and 3D struc-tures inside the fused silica, which are in excellent agreement with the simulation results. The experimental results of the "H-U-S-T" structure demonstrate that customized arbitrary intensity distribution inside the material can be realized. (c) 2023 Optica Publishing Group