Fabrication of a diamond concave microlens array for laser beam homogenization

•A diamond concave microlens array was realized through a chemical reflow method.•The microlens array has a well-uniformity and low surface smoothness of 0.908 nm.•The microlens array exhibited excellent imaging and focusing performances.•The performance of homogenization by the microlens array was successfully realized. An ultra-smooth diamond concave microlens array was realized using a chemical reflow process assisted by dry etching technique, which has a great performance for homogenization of light beam. Firstly, photolithography was used to produce a regular hexagonal hole array in the photoresist layer on a diamond substrate. Then, the hole array was reflowed in ethanol solvent vapor atmosphere at 20 ℃ to form the concave spherical structure array. Finally, diamond concave microlens array was formed by transferring photoresist concave structures onto diamond substrate through dry etching technique. The fabricated diamond concave microlens array was characterized, demonstrating a well-uniformity of the surface morphology, high quality imaging and focusing performances. Furthermore, laser beam homogenization was realized by the diamond concave microlens array.