John W. Franks (a), Thomas Hingant (b), Paul Vervoort (c)a - Umicore Electro-Optic Materials, Kinnoull Street, Dundee DD2 3ED, b - Umicore IR Glass, ZA du Boulais, 35690 Acigné, France; c - Umicore EOM NV, Watertorenstraat 33, B2250 Olen, Belgium;