Deposition of Ge-doped silica thin films for an integrated optic application using a matrix distributed electron cyclotron resonance PECVD reactor Roelene Botha a, * ,1 , Pavel V. Bulkin b , Pieter L. Swart a a Center for Optical Communications and Sensors, Faculty of Engineering and the Built Environment, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa b Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, 91128 Palaiseau Cedex, France Received 28 February 2006; accepted 8 November 2006 Available online 22 January 2007 Abstract Optical quality Ge-doped SiO 2 thin films, suitable for an integrated optic version of a gain equalizer for erbium-doped fibre amplifiers (EDFAs), have been deposited using a matrix distributed electron cyclotron resonance plasma-enhanced chemical vapour deposition (MDECR-PECVD) system. Using spectroscopic ellipsometry and infrared transmission spectroscopy, the optical constants and hydro- xyl content of the films were calculated. Losses due to the hydroxyl overtone at 1.37 lm are found to be approximately 0.251 dB/cm. An RBS analysis determined the germanium content of the films to be in the vicinity of 4 at.%. A comparison of the atomic percentage of germanium in the films and their corresponding refractive indices with values obtained using other deposition methods is also discussed. Ó 2006 Elsevier B.V. All rights reserved. PACS: 42.70.a; 78.20.Ci; 81.15.Gh Keywords: Optical materials; Optical constants; Plasma-enhanced; Chemical vapour deposition 1. Introduction Germanium-doped silica is widely used as core material for optical fibres and planar waveguides. It offers high transmission in the infrared and visible wavelength range and is photosensitive to UV light [1,2] and can be made into waveguides with characteristics similar to single-mode fibres. A variety of deposition techniques for waveguide layers have been developed, such as the sol–gel technique [3], plasma-enhanced chemical vapour deposition (PECVD) [4], hollow cathode PECVD [5] and flame hydrolsysis deposition (FHD) [6]. Matrix distributed elec- tron-cyclotron resonance plasma-enhanced chemical vapour deposition (MDECR-PECVD) technology offers all the benefits of a conventional PECVD system, such as good controllability of the film thickness and optical con- stants at low temperatures (<300 °C) when compared to techniques such as FHD, making it an excellent choice for deposition of optical waveguide layers on tempera- ture-sensitive substrates. It offers high growth rate and wide flexibility in terms of the chemical composition. In addition, MDECR-PECVD gives the added possibility of virtually unlimited scaling of the deposition area [7]. Previ- ously, a tuneable gain equalizer for EDFAs has been designed and implemented in optical fibre, as described in [8], for example. However, it is not perfect due to the inter- ference noise caused by the Mach–Zehnder interferometer (MZI) configuration, which forms part of the device. An integrated optic version of the tuneable gain equalizer has 0925-3467/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2006.11.055 * Corresponding author. Tel.: +33 0 169333217. E-mail address: botha@poly.polytechnique.fr (R. Botha). 1 Currently working towards a PhD degree at the LPICM, Ecole Polytechnique, 91128 Palaiseau, France. www.elsevier.com/locate/optmat Optical Materials 30 (2007) 244–247