Fabrication of Fresnel zone plate lens in fused silica glass using femtosecond laser lithography technology

Abstract

This paper demonstrates mask-less formation of Fresnel zone plate lens on the surface of a fused silica glass substrate using femtosecond laser lithography technology. The lens consists of a series of concentric rings, which has been fabricated on the glass surface by femtosecond laser writing followed by chemical etching and stripping. We also pattern Fresnel zone plate on fused silica glass surface using direct femtosecond laser writing technique. The both Fresnel zone plate lenses have a focal length of 50 mm. Femtosecond laser lithography technique offers smooth patterning of materials compared to traditional femtosecond laser writing. Consequently, femtosecond laser lithography induced Fresnel zone plate lens yields considerably high diffraction efficiency. Using these Fresnel zone plate lenses, we are able to observe the micro-letters, micro-machined on aluminum coated poly-methylmethacrylate (PMMA) surface indicating excellent focusing and imaging capability of the Fresnel zone plate lenses. The proposed mask-less technology is simple compared to other lithography techniques, which shows great potential for small-scale manufacturing of similar kinds of optical devices.