Rapid fabrication of large-area concave microlens arrays on silica glasses by femtosecond laser bursts.

An efficient and flexible method using femtosecond laser bursts assisted by wet etching is presented to fabricate large-area high-quality microlens arrays (MLAs) on a silica glass surface. In this method, femtosecond laser bursts can ablate micro craters on silica glass in a fast, single-step process by controlling the electron density and a high-speed scanning galvanometer, and the influence mechanism of the number of pulses within a burst on the accuracy and quality of micro craters is analyzed in detail. The experimental results show that the preparation efficiency of micro craters is significantly improved to approximately 32,700 per second. By subsequent acid etching, concave microlenses with controllable dimensions, shapes, and alignments are easily obtained. A large area close-packed hexagonal concave MLA is successfully fabricated by using this method and shows high surface quality and uniformity, which excellently demonstrates the feasibility and flexibility of rapidly fabricating MLAs in the burst regime.