Excimer laser micromachining of aspheric microlens arrays based on optimal contour mask design and laser dragging method

Abstract

This paper presents an improved excimer laser micromachining method for fabricating arrayed microstructures with a predesigned surface profile. The proposed method is developed from a conventional biaxial laser dragging method, but numerical analysis and optimal pattern design on the contour mask are introduced so that the machined surface profiles can be well controlled and matched to the designed profiles. To demonstrate the capability of this new approach, an array of aspheric microlenses that have analog surfaces for minimizing the focal spot sizes of the lenses is designed and fabricated. An array of 10×10 microlenses with an aperture size of 100 μm and a designed aspheric profile are obtained experimentally. The machined surface profiles are closely matched to their designed ones, with a profile deviation of less than 1 μm. Furthermore, the machined surfaces are smooth, with an average surface roughness of around 2 nm. Optical measurements on these machined aspheric microlenses show minimized focal spot sizes approaching their optical diffraction limits.