Solution‐Repair‐Assisted Femtosecond Laser Crystallization of Fluoroaluminate Glass for Customized UV–Visible–Infrared Brittle Micro‐Diffractive Optics

Abstract

A novel solution‐repair‐assisted femtosecond laser crystallization method is reported for Fluoroaluminate (AlF3) glass, with exceptional ultraviolet–visible‐mid‐infrared transmission characteristics, for fabricating wide‐wavelength micro‐optical elements. This innovative approach achieves remarkable optical quality through amorphous‐to‐crystalline phase transition, effectively mitigating the longstanding challenge of surface roughness in laser‐processed brittle materials. A systematic investigation is conducted into the effects of various laser parameters (e.g., laser energy, repetition rate, and scanning velocity) on the fabricated AlF3 glass microstructure after crystallization. Leveraging these data, diverse micro‐diffractive optical elements are successfully fabricated on AlF3 glass, including 1D and 2D gratings with tunable duty cycles, square grating, circular grating, and Dammann grating. All these elements demonstrated exceptional optical diffraction performance. Additionally, by implementing precise control of structural features, a regulated micro‐diffractive optical device with tailored structural dimensions is designed and fabricated. As a demonstration, a Fresnel zone plate (FZP) with varying widths and radii for each concentric circle is fabricated, achieving a fabrication error below 1 µm. The focusing and imaging performance of AlF3 glass FZP is validated across ultraviolet, visible and infrared wavelengths, showcasing its superior optical capabilities. This work establishes a new paradigm for the fabrication of wide‐wavelength brittle micro‐optical elements and opens new possibilities for multi‐spectrum photonics.