Fabrication of hexagonally arrayed micro-structures with axially symmetrical surface profile by tri-axial excimer laser scanning

This paper presents an excimer laser contour scanning method for achieving hexagonally arrayed micro-structures with an axially symmetrical surface profile. It utilizes a specially designed contour mask for projected laser scanning along three different directions separated by 120 on the surface of a sample. Through rigorous analysis, a new contour mask design method is proposed which guarantees not only the profile accuracy but also the axial-symmetry of machined micro-structures. Experiments have been carried out using a 248 nm KrF excimer laser micromachining system. Hexagonal arrays of micro-lenses with an aperture size of 100 μm in diameter and a maximum sag height from 15 to 30 μm are successfully produced using designed contour masks. The machined profile accuracy is better than ±0.5 μm within most of the central area of lens aperture. The flexibility on machined surface profile and its machining accuracy allow new types of micro-lens arrays with specific optical functions and new applications in the future.