DIFFRACTIVE MICROLENSES REPLICATED IN FUSED-SILICA FOR EXCIMER LASER-BEAM HOMOGENIZING

A diffractive beam homogenizer, based on an array of square, off-axis, continuous-relief diffractive microlenses, for use with an excimer la ser has been studied. We originally fabricated the homogenizer by dire ct-write electron-beam lithography, from which we made replicas in UV- grade fused silica by hot embossing and reactive ion etching. Atomic f orce microscopy measurements of original and replicated elements showe d the accuracy of the replication fidelity. One of the replicated homo genizers was evaluated together with a KrF excimer laser. The homogeni zed beam had a flat-top profile with 31% of the beam energy contained within an area where the beam intensity was above a threshold level of 90% of the maximum intensity. (C) 1997 Optical Society of America.