Maskless Fabrication of Honeycomb Random Microlens Array by a Femtosecond Laser

Abstract

A rapid and maskless method is proposed to fabricate a honeycomb random microlens array (rMLA) on silica glasses surface. The micro-crater array is ablated by a femtosecond laser using a point-by-point multiple scanning process. By subsequent acid etching, the rMLAs with different arrangements, diameters and depths can be easily obtained. The relationships between the processing parameters and the morphologies of the rMLAs were analyzed in detail. We designed and successfully fabricated the hexagonal-arranged rMLA and square-arranged rMLA by using this method. The homogenizing experiments have demonstrated that the fabricated rMLAs can break the periodicity of the traditional periodic microlens array (pMLA) and improve the uniformity of the high-coherence laser homogenized spot. It exhibited excellently that two types of the rMLAs had good homogenizing property (more than 86%) and high energy utilization rate (more than 87%). The proposed technology might provide an efficient and new method to simply fabricate large-area close-packed rMLAs on silica glass.

Keywords: femtosecond laser, Random microlens array, Chemical etching, Laser beam homogenization, Energy utilization rate