Broadband NIR emission in novel sol–gel Er 3+ -doped SiO 2 –Nb 2 O 5 glass ceramic planar waveguides for photonic applications Felipe Thomaz Aquino a , Jefferson Luis Ferrari a,b , Sidney José Lima Ribeiro c , Alban Ferrier d , Philippe Goldner d , Rogéria Rocha Gonçalves a,⇑ a Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, CEP 14040-901, Ribeirão Preto, SP, Brazil b Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, São João Del Rei, MG 36301-160, Brazil c Laboratório de Materiais Fotônicos, Instituto de Química, UNESP, Caixa Postal 355, Araraquara, SP 14801-970, Brazil d Chimie-Paristech, Laboratoire de Chimie de la Matière Condensée de Paris, CNRS-UMR 7574, UPMC Univ. Paris 06, 11 rue Pierre et Marie Curie, 75005 Paris, France article info Article history: Received 2 August 2012 Received in revised form 13 September 2012 Accepted 13 September 2012 Available online 1 November 2012 Keywords: Waveguides Sol–gel NIR emission Niobium oxide Optical properties Photonics abstract This paper reports on the sol–gel preparation and structural and optical characterization of new Er 3+ - doped SiO 2 –Nb 2 O 5 nanocomposite planar waveguides. Erbium-doped (100-x)SiO 2 –xNb 2 O 5 waveguides were deposited on silica-on-silicon substrates and Si(1 0 0) by the dip-coating technique. The waveguides exhibited uniform refractive index distribution across the thickness, efficient light injection at 1538 nm, and low losses at 632 and 1538 nm. The band-gap values lied between 4.12 eV and 3.55 eV for W1–W5, respectively, showing an excellent transparency in the visible and near infrared region for the wave- guides. Fourier Transform Infrared (FTIR) Spectroscopy analysis evidenced SiO 2 –Nb 2 O 5 nanocomposite formation with controlled phase separation in the films. The HRTEM and XRD analyses revealed Nb 2 O 5 orthorhombic T-phase nanocrystals dispersed in a silica-based host. Photoluminescence (PL) analysis showed a broad band emission at 1531 nm, assigned to the 4 I 13/2 ? 4 I 15/2 transition of the Er 3+ ions pres- ent in the nanocomposite, with a full-width at half medium of 48–68 nm, depending on the niobium con- tent and annealing. Hence, these waveguides are excellent candidates for application in integrated optics, especially in EDWA and WDM devices. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The growing demand for faster internet and telecommunication networks has aroused researcher’s interest in materials for pho- tonic applications [1–11]. Over the last years, erbium-doped mate- rials such as Erbium-Doped Fiber Waveguide Amplifiers (EDFAs) and Erbium-Doped Planar Waveguide Amplifiers (EDPWAs) have received increasing attention [1–3], especially for use in integrated photonic systems. The development of planar integrated circuits allows combination of properties like switching, guiding, wave- length-division multiplexing (WDM), splitting, light amplification, and low losses, among others [2]. In this sense, the study of optical properties of rare-earth doped thin films represents a fundamental step in the development of new active components such as optical amplifiers [2–9]. The preparation of more compact optical amplifi- cation systems (EDPWAs) leads to significant size reduction as compared to their predecessors, the so-called Erbium-Doped Fiber Amplifiers (EDFAs), and higher concentrations of rare earth ions are employed. Thus, monitoring the photophysical properties of the films and relating them to the structural properties is an important point when it comes evaluating the potential of novel materials for this photonic application [2–9,12]. When Er 3+ ions are incorporated into an adequate host, an effi- cient emission from the first excited state to the ground state ( 4 I 13/2 ? 4 I 15/2 ) takes place in the near infrared (NIR) region, namely around 1550 nm. This is exactly the region that is used in telecommunication for information transmission [1,2], the so- called C-telecom band. In addition, it is well known that a broad and flat emission band is required for amplifiers and WDM devices, since they can operate in a large wavelength range. In fact, nowa- days great attention has been focused on the development of tele- communication devices for the WDM network system, which can operate not only in the C but also in the S and L telecommunication bands. As a result, there has been growing interest in the produc- tion of optical planar waveguide amplifiers based on rare earth- activated glasses or glass ceramics, which exhibit a broadband NIR emission [1,9,13], mainly for local area network (LAN) applications. Most of the literature results concern utilization of Er 3+ -doped glasses and glass ceramics in the C-telecom band, but depending 0925-3467/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.optmat.2012.09.029 ⇑ Corresponding author. Tel.: +55 16 36024851; fax: +55 16 36338151. E-mail address: rrgoncalves@ffclrp.usp.br (R.R. Gonçalves). Optical Materials 35 (2013) 387–396 Contents lists available at SciVerse ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat