Fabrication of chalcogenide glass based hexagonal gapless microlens arrays via combining femtosecond laser assist chemical etching and precision glass molding processes

Chalcogenide glasses (ChGs) are emerging as critical infrared (IR)-enabled materials in advanced IR optical systems by the wealth of their transparency in the key wide infrared (IR) transmission window. However, fabrication of ChG-based integrated micro-optical components in an efficient and economical way remains a huge challenge. In this paper, a 3D close-packed hexagonal microlens array (MLA) possessing over 6000 convex hexagonal micro-lenslets with the size of tens of micrometers within a footprint of 10 mm × 10 mm on a Ge₂₀Sb₁₅Se₆₅ ChG surface was successfully fabricated via a precise thermal-mechanical molding process. The master mold of ChG MLA was firstly fabricated by a femtosecond laser-assisted chemical etching process and then transferred on to the surface of the ChG via a precision thermo-mechanical molding process, which resulted in a convex MLA. The morphology, imaging and focusing performances of the as-prepared ChG MLA were investigated and demonstrated the advancement of the method. Meanwhile, the IR transmittance and x-ray diffraction image of the ChG MLAs were measured to verify the structural and compositional stability of the ChG under the given molding conditions. The combined results proved a new route to mass production of miniaturized gapless ChG MLAs for advanced infrared micro-optics.