Phase-Type Fresnel Zone Plate with Multi-Wavelength Imaging Embedded in Fluoroaluminate Glass Fabricated via Ultraviolet Femtosecond Laser Lithography

Abstract

Herein, we report a novel optical glass material, fluoroaluminate (AlF3) glass, with excellent optical transmittance from ultraviolet to infrared wavelength ranges, which provides more options for application in optical devices. Based on its performance, the phase-type Fresnel zone plate (FZP) by ultraviolet femtosecond (fs) laser-inscribed lithography is achieved, which induces the refractive index change by fs-laser tailoring. The realization of ultraviolet fs-laser fabrication inside glass can benefit from the excellent optical performance of the AlF3 glass. Compared with traditional surface-etching micro-optical elements, the phase-type FZP based on AlF3 glass exhibits a clear and well-defined geometry and presents perfect environmental suitability without surface roughness problems. Additionally, optical focusing and multi-wavelength imaging can be easily obtained. Phase-type FZP embedded in AlF3 glass has great potential applications in the imaging and focusing in glass-integrated photonics, especially for the ultraviolet wavelength range.

Femtosecond Laser Fabrication of Refractive/Diffractive Micro‐Optical Components on Hard Brittle Materials

“…Volume FZPs were prepared by laser‐induced refractive index change or void generation in fused silica, [ 105 ] sapphire, [ 106 ] borosilicate glass, [ 107 ] and fluoroaluminate glass. [ 108 ] Most of the initial studies focused on fused silica materials. In 2002, the direct laser writing of the FZP was first reported.…”

“…The phase‐type FZP in fluoroaluminate glass has precise geometry and good environmental adaptability. [ 108 ] In addition, it achieves optical focusing and multiwavelength imaging, as shown in Figure 10b. And fluorotellurite glass is a potential alternative material for micro‐optics in NIR band applications.…”

“…Adapted with permission. [ 108 ] Copyright 2021, MDPI. c) Sapphire surface FZP with excellent surface quality and geometry.…”

Imaging/nonimaging microoptical elements and stereoscopic systems based on femtosecond laser direct writing

“…Owing to the instantaneous high-intensity energy of the femtosecond laser, high-precision machining of hard and brittle materials can be achieved using FLA combined with several auxiliary methods in section of "Processing principle of FLA". Graphene oxide [150][151][152] , optical glass 137,153,154 , and crystals (such as sapphire 71,155 and silicon 146,[156][157][158] ) are the most widely used laser-ablative materials. These materials have excellent physical and chemical stabilities, including high hardness, hightemperature resistance, and corrosion resistance, and are widely used in extreme fields, such as the military and aerospace industries.…”