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Optical properties of directly excited erbium (Er3+) ions have been studied in silicon rich silicon oxide materials codoped with Er3+. The spectral dependence of the direct excitation cross section (σdir) of the Er3+ atomic 4I15/2→4I11/2 transition (around 0.98 μm) has been measured by time resolved μ-photoluminescence measurements. We have determined that σdir is 9.0±1.5×10-21 cm2 at 983 nm, at least twice larger than the value determined on a stoichiometric SiO2 matrix. This result, in combination with a measurement of the population of excited Er3+ as a function of the pumping flux, has allowed quantifying accurately the amount of optically active Er3+. This concentration is, in the best of the cases, 26% of the total Er population measured by secondary ion mass spectrometry, which means that only this percentage could provide optical gain in an eventual optical amplifier based on this material. [ABSTRACT FROM AUTHOR]

Pump and probe experiments on Er3+ ions coupled to Si nanoclusters have been performed in rib-loaded waveguides to investigate optical amplification at 1.5 μm. Rib-loaded waveguides were obtained by photolithographic and reactive ion etching of Er-doped silica layers containing Si nanoclusters grown by reactive sputtering. Insertion losses measurements in the infrared erbium absorption region allowed to gauge an Er3+ absorption cross section of about 5×10-21 cm2 at 1534 nm. Signal transmission under optical pumping at 1310 nm shows confined carrier absorption of the Si nanoclusters. Amplification experiments at 1535 nm evidence two pump power regimes: Losses due to confined carrier absorption in the Si nanoclusters at low pump powers and signal enhancement at high pump powers. For strong optical pumping, signal enhancement of about 1.2 dB/cm was obtained. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present the state of the art of our work to obtain an infrared optical amplifier in which Er3+ doped SiO2 sensitised with Si nanoclusters (Si-nc) act as the active material to provide the signal amplification. As a result of a careful optimisation of the deposition parameters we have achieved that the Er3+ fraction coupled with the Si-nc with respect to the total optically active Er3+ content is about 23%. This result has been determined both by quantitative measurements of the first excited state population and by pump and probe amplification measurements under non-resonant pumping, where 1dBcm−1 of internal gain (reduction of 2dBcm−1 of the initial absorption losses) has been obtained. We will discuss several material issues that are mandatory to address and then overcome in order to optimise the fraction of Er3+ coupled to Si-nc, with the aim of exciting all the ions through indirect transfer. In particular we will address: carrier absorption (CA) in Si-nc, cooperative up-conversion and non-radiative recombination in Er3+, together with the distance dependent interaction and Auger back-transfer processes in the Er/Si-nc coupled system. [Copyright &y& Elsevier]

Abstract: We present a electroluminescence (EL) study of the Si-rich silicon oxide (SRSO) LEDs with and without Er3+ ions under different polarization schemes: direct current (DC) and pulsed voltage (PV). The power efficiency of the devices and their main optical limitations are presented. We show that under PV polarization scheme, the devices achieve one order of magnitude superior performance in comparison with DC. Time-resolved measurements have shown that this enhancement is met only for active layers in which annealing temperature is high enough (>1000°C) for silicon nanocrystal (Si-nc) formation. Modeling of the system with rate equations has been done and excitation cross-sections for both Si-nc and Er3+ ions have been extracted. [Copyright &y& Elsevier]

Abstract: In this work we will give an overview of the optical properties of Si nanoclusters coupled to Er3+ ions in SiO2 matrices produced by reactive magnetron co-sputtering. We have divided the work into two separate studies realised on the same samples, which are the result of a thorough optimisation work. The first one have been realised in order to get a clear picture of the interaction mechanism. On the second we will show a quantitative evaluation of the potential performances from a material point of view (determination of the whole optically active Er3+ content, excitable by direct or indirect means) and actual performance in a waveguide device (determination of internal gain values). [Copyright &y& Elsevier]