| Addressing the existing challenges of low transmission and high absorption rates in near-infrared wavelength laser lenses, coupled with difficult fabrication processes, this study employs Si3N4 as the material. Compared to traditional silicon photonics technology, Si3N4 offers advantages such as lower loss, a broader transparent window, and higher power handling capability. Furthermore, Si3N4 is compatible with CMOS manufacturing processes, facilitating large-scale integration and production. Therefore, this paper proposes a polarization-insensitive metalens using low-refractive-index silicon dioxide as the substrate and high-transmittance silicon nitride as the phase-modulating basic unit, designed for an operating wavelength of 780 nm. The optical properties of the metamaterial lens unit structure were analyzed and parameters optimized using Finite Element Method (FEM) simulation software. The average transmission rate reached 93.74%. The simulated focal length of the designed device was 6.0059 μm, with an error of only 0.098% compared to the design value. The focusing efficiency reached 68.86%, The full width at half maximum (FWHM) was 735.2 nm, with the spot size approaching the diffraction limit. Subsequent analysis demonstrated that metamaterial lenses with varying focal lengths while maintaining a fixed aperture still exhibited excellent focusing performance, with all focusing efficiencies exceeding 68.3%. This design advances the development of lightweight, planar lenses, reduces manufacturing costs, and holds broad application prospects in the field of lasers. |
