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

Abstract

This paper expresses maskless formation of Fresnel zone plate (FZP) lens on fused silica glass surface using femtosecond laser lithography technology. The FZP lens consists of a series of concentric rings that has been encoded on a glass surface using femtosecond laser irradiation followed by chemical etching and stripping. To compare the performance of the FZP lens with traditional laser induced FZP, we also fabricated FZP on the surface of and inside fused silica glass using femtosecond laser direct writing. In all the cases, the FZP lenses have a focal length of 50 mm. In addition, we fabricated a 25-mm focal length FZP lens by means of femtosecond laser lithography. Compared to traditional femtosecond laser direct writing, femtosecond laser lithography technique offers smooth patterning of materials. Consequently, femtosecond laser lithography engraved FZP lens yields considerably higher diffraction efficiency. Besides, we investigated the diffraction pattern of the fabricated FZP lenses. Using these FZP lenses, we are able to observe microletters encoded on an aluminum coated poly-methylmethacrylate surface indicating excellent focusing and imaging capability of the FZP lenses. The proposed maskless technology is simple compared to other lithography techniques, representing great potential for small-scale manufacturing of similar kinds of optical/photonics devices.