Two-dimensional array of diffractive microlenses fabricated by thin film deposition

A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested. Each lenslet has a rectangular aperture and a size of 1.5 mm x 1.5 mm. The focal length of each lenslet is 47 mm. The array was produced by depositing thin films of silicon monoxide on a quartz glass substrate and by using photolithographic techniques. The performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP). The FZP pattern was implemented as a phase structure with eight discrete levels. The diffraction efficiency was measured to be 91%.