Design and fabrication of on-fiber diffractive elements for fiber-waveguide coupling by means of e-beam lithography

The aim of this paper is to demonstrate that efficient fiber-waveguide optical coupling can be achieved using a multilevel phase diffractive element (PDE) fabricated directly on the top of the fiber by means of e-beam lithography. The diffractive phase element is calculated to focus and reshape the gaussian symmetric beam exiting a single-mode fiber into a desired asymmetric intensity distribution at the waveguide input plane. Phase modulation is obtained by multilevel profiling a polymeric material coated on the top of the fiber by means of a specific fabrication process including e-beam. lithography and chemical etching. Experimental results obtained for fiber-waveguide coupling with a 20-mum diameter diffractive element are also presented. (C) 2003 Elsevier Science B.V. All rights reserved.