Fabrication of large-aperture lightweight diffractive lenses for use in space

We describe the advantages of using diffractive (Fresnel) lenses on thin me mbranes over conventional optics for, among others, future space telescope projects. Fabrication methods are presented for lenses on two types of free standing membrane up to 50 cm in size. The first is a Fresnel lens etched i nto a thin (380-mum) glass sheet, and the second is an similar to 50-mum-th ick polymer membrane containing a Fresnel lens made by replication process from a specially made fused-silica master. We show optical performance anal ysis of all the lenses that are fabricated, including a diffraction-limited Airy spot from a 20-m-focal-length membrane lens in a diffractive telescop e system. (C) 2001 Optical Society of America.