Direct nano-patterning methods using nonlinear absorption in photopolymerization induced by a femtosecond laser

Abstract

Investigation into the methods of direct fabrication for submicron-detailed patterns without the use of any photomask was carried out using two-photon polymerization (TPP). Some patterns can be fabricated easily in the range of several micrometers by solidifying inside a photopolymerizable resin by a scanning process using a volume-pixel (voxel) matrix that is transformed from a bitmap figure file. The voxels are generated consecutively to merge into adjoining voxels in the process of fabricating a pattern. The resolution of a fabricated pattern can be obtained under the diffraction limit of a laser beam due to the nonlinear absorption phenomenon. In this paper, a top-down reverse building technique was introduced to fabricate a polymeric pattern on a metal layer. Also, a contour offset algorithm (COA) and a beam expanding method have been attempted to make precise patterns and to enlarge the working area. Through this work, several patterns for various applications on nano- and microtechnology were fabricated on a glass plate and a thin metal layer to demonstrate the usefulness of the developed algorithm.