Tm-Er codoping Al 2 O 3 Thin Films: Activation by Annealing
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V5.6.1/FF5.6.1
Tm-Er codoping Al2O3 Thin Films: Activation by Annealing Zhisong Xiao, R. Serna, C. N. Afonso, and I. Vickridge1 Instituto de Optica, CSIC, Serrano 121, 28006 Madrid, Spain, 1 Institut de NanoSciences de Paris, UMR 7588 du CNRS, Universite de Paris 6 et 7, 2, Place Jussieu, 75251 Paris Cedex 05, France ABSTRACT Amorphous aluminum oxide (Al2O3) thin films codoped with Tm3+ and Er3+ have been prepared by pulsed laser deposition. A broad emission band with a full-width half maximum (FWHM) up to 230 nm was observed in Tm-Er codoped film. The spectrum shows two peaks located at 1540 nm corresponding to Er3+ emission and 1640 nm due to Tm3+ emission. The luminescence intensity dependence on the annealing temperature was investigated. It is shown that the annealing temperature and energy transfer between Tm3+ and Er3+ ions play an important role in the definition of the luminescent response. INTRODUCTION Integrated optoelectronic circuits require the development of light sources and optical amplifiers in planar waveguides. Rare earth (RE) doping of dielectrics allows preparing suitable materials for these applications. [1, 2] Moreover, there is a great effort to develop devices for wavelength-division-multiplexing (WDM) in local network systems, and a high demand for optical amplifiers operated at 1.4 ~ 1.7 µm to extend the present silica-based erbium (Er) doped amplifiers range (1530-1600 nm). [3, 4] It is thus interesting to explore the possibility of profiting from emission of more than one kind of RE ion in a single integrated device. Tm3+ is promising as a complement to Er3+ (emission at 1.54 µm) due to its emission bands around 1.47 µm and 1.6-1.8 µm. [5, 6] Moreover, for waveguide devices there is an attractive alternative based on the use of Al2O3. The development of waveguide technology has been explored as the high contrast between the refractive index of Al2O3 and that of the SiO2 cladding layer (∼0.2) leads to a high confinement of the guided light, making possible smaller device structures. In our previous works we have shown that alternate pulsed laser deposition (PLD) from the host (a-Al2O3) and dopant (RE) targets can be used to obtain artificial structures in which the RE concentration and ion-ion separation are controlled in the nanometer scale. [7, 8] We have found two Tm3+ emission bands peaked at 1.48 µm and 1.64 µm from the Tm-only doped Al2O3 thin films. The aim of this work is to explore ways to improve the width and efficiency of both Er3+ and Tm3+ luminescence in Tm-Er: Al2O3 thin films by the choice of an appropriate thermal annealing procedure.
V5.6.2/FF5.6.2
EXPERIMENTAL DETAILS An ArF excimer laser (λ = 193 nm, τ = 20 ns full width at half maximum) was used to ablate independently the Al2O3 and RE targets. The Er and Tm ions were always deposited on Al2O3 layers, and only one pulse at an average energy density of 2 Jcm-2 were used to ablate RE targets. The thickness of the spacing Al2O3 layers was controlled in the nanometer range. The Er-Er in-depth separation was designed
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