Ag þ –Na þ ion exchange from dilute melt: guidelines for planar waveguide fabrication on a commercial phosphate glass G. Jose a , G. Sorbello b, * , S. Taccheo a , G. Della Valle a , E. Cianci c , V. Foglietti c , P. Laporta a a INFM-Dipartimento di Fisica del Politecnico di Milano and Istituto di Fotonica e Nanotecnologie-CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy b Dipartimento di Ingegneria Informatica e delle Telecomunicazioni, University of Catania, Viale A. Doria 6, Catania 95125, Italy c Istituto di Fotonica e Nanotecnologie-CNR, Via Cineto Romano 42, 00156 Roma, Italy Received 24 June 2002; received in revised form 13 December 2002; accepted 6 January 2003 Abstract Silver–sodium ion-exchanged waveguides on Schott IOG-1 erbium–ytterbium-doped phosphate glass have been fabricated and characterized. Ion exchange by thermal diffusion from a ternary salt melt (AgNO 3 , NaNO 3 and KNO 3 ) has been carried out by varying the process parameters such as melt composition, temperature and diffusion time. Guidelinesaregiventooptimizetheactivewaveguidesforafullcompatibilitywithstandardsinglemodeopticalfibres. Ó 2003 Elsevier B.V. All rights reserved. PACS: 42.70.C; 42.82; 42.82.E Keywords: Er-doped glasses; Active waveguide; Silver–sodium ion exchange 1. Introduction Integrated planar lightwave circuits are an in- teresting solution to the increasing density of optical devices in modern all-optical wavelength- division networks. A number of fabrication pro- cesses have been thoroughly investigated during the years, namely, ion exchange [1], plasma en- hanced chemical vapor deposition [2], glass on silicon [3,4], silicon photonic circuits (Si–SiO 2 ) [5], sol–gel [6], in-diffusion on lithium niobate sub- strate [7,8], thin film sputtering [9] and femtosec- ond laser writing [10]. Among these, the ion exchange technique is nowadays attracting renewed interest for its sim- plicity, flexibility and low fabrication cost. In the field of active waveguide for optical commu- nications, erbium and erbium–ytterbium-doped phosphate and silicate glass hosts, suitable for ion- exchange, have been recently developed by several groups [11–14]. Moreover, low-cost hybrid sub- strates that allow the integration of active and passive optical components on a single chip have been recently fabricated [15]. Among different glass hosts, phosphate glasses, thanks to their high * Corresponding author. Tel.: +39-095-738-2351; fax: +39- 02-700-401-453. E-mail address: gino.sorbello@diit.unict.it (G. Sorbello). 0925-3467/03/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0925-3467(03)00021-1 Optical Materials 23 (2003) 559–567 www.elsevier.com/locate/optmat