Erbium/Ytterbium co-doped Glass Thin Film Waveguides

Current trend in the photonic components market is to provide more bandwidth at reasonable cost using the existing fiber based optical technology. However, there is an increasing research and development in the area of distribution network, where the metropolitan and local area networks (MAN, LAN) are evolving to meet the demand for data distribution towards the final customer. Therefore, it is necessary to provide devices which are reliable, reduce power penalty significantly and provide multiple functions by combining both the active and passive functionalities. Planar technology may offer some solution to these requests and represents one of the most significant optical technologies in telecommunications. Rare-earth doped materials, widely employed in Erbium-Doped-Fiber Amplifiers (EDFAs) and solid state lasers, are of crucial importance for developments in integrated optics (IO). In particular, Erbium-doped waveguide amplifiers (EDWAs) are promising candidates for IO circuits operating in MAN. Integrated optical amplifiers should be as short as possible, so that much higher rare-earth concentrations are required than in EDFAs. When only Er3+ ions are present in short waveguides, the pumping at 980 nm is not very efficient, since the Er3+ absorption cross-section at this wavelength is not very high. This problem can be alleviated by the addition of Yb3+ as a sensitizing ion, because the absorption cross section of the Yb3+ 2F5/2 ? 2F7/2 transition is about ten times higher than that of Er3+ 4I11/2 ? 4I15/2. Lately, laser action and 5 dB maximum net gain at 1536 nm has been achieved in silica-based waveguides doped with erbium and ytterbium [1]. The key requirements for developing EDWAs are: i) refractive index and thickness of the film have to be tailored, in order to satisfy both single-mode condition at 1.5 ?m and efficient coupling to fibers; ii) the structural and optical homogeneity have to be optimized, in order to reduce losses and rare-earth clustering; iii) the OH groups must be effectively removed, because the 4I13/2 luminescence of OH--coordinated Er3+ ions is completely quenched by two phonon-OH mechanism. This lecture presents some results in Er or Er/Yb-doped silica-based planar waveguides prepared by three different technological routes: sol-gel, ion-exhange and rf-sputtering [1-3]. Optical and spectroscopic assessment of the different systems are reported as well as some preliminary example of rib waveguides produced by photolithography and etching process.