Direct fabrication of seamless roller molds with gapless and shaped-controlled concave microlens arrays

This Letter demonstrates the direct fabrication of gapless concave microlenses on glass cylinders, which can be used as seamless roller molds for the continuous imprinting of large-area microlens arrays. The method involves femtosecond laser exposures followed by a chemical wet-etching process. A honeycomb-like concave microlens array was fabricated on a glass cylinder with a diameter of 3 mm. We demonstrated the flexibility of the method in tuning the shape and depth of the concave structures by the arrangements of the laser exposure spots and laser powers, and examined the replicating ability of the roller mold by the polymer castling method.