A subwavelength-scale square lattice optical nanostructure is fabricated using an interference photolithography process on the surface of a quartz microlens array. This nanostructuring of the quartz surface introduces an antireflective effect, reducing reflectivity between 10% and 30% and enhancing the transmissivity 3% in the visible spectrum. This approach permits fast fabrication on a 4-inch wafer covered with microlenses (non-flat surface) and produces monolithic devices which are robust to adverse environments such as temperature variations. [DOI: 10.2971/jeos.2010.10006]