Fabrication of bifocal lenses using resin that can be processed by electron beam lithography after ultraviolet-nanoimprint lithography

Optical lenses with multiple focal points are expected to have applications in fields such as medical imaging. As a method to efficiently fabricate these structures, we propose a two-step lithography method that uses an electron beam resist capable of ultraviolet-nanoimprint lithography (UV-NIL) that was developed in our laboratory. Using this method, a microlens array is prepared by UV-NIL and a concentric-circle microlens having a different focal point from the microlens is prepared by electron beam lithography (EBL). This makes it possible to achieve two focal points, the focal point of the microlens and the focal point of the concentric-circle microlens. Furthermore, using this lens as a mold, an inversion pattern is produced again with UV-NIL. It was confirmed that the lens has a focal point of 3 mm by the microlens array and of 8 mm by the concentric-circle microlens. In this study, we create a microlens array with UV-NIL and expose the concentric pattern to the lens area with EBL to create a bifocal lens.