22 May 2007 Non-linear optical properties of PECVD Si-nc under nanosecond excitation
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Proceedings Volume 6591, Nanotechnology III; 65910A (2007); doi: 10.1117/12.721955
Event: Microtechnologies for the New Millennium, 2007, Maspalomas, Gran Canaria, Spain
Abstract
A study of the non-linear optical properties of Si-nc embedded in SiO2 has been performed by using the z-scan method in the nanosecond and femtosecond ranges. Substoichiometric SiOx films were grown by plasma-enhanced chemical-vapor deposition (PECVD) on silica substrates for Si excesses up to 24 at. %. An annealing at 1250 °C for 1 hour was performed in order to precipitate Si-nc, as shown by EFTEM images. Z-scan results have shown that, by using 5-ns pulses, the non-linear process is ruled by thermal effects and only a negative contribution can be observed in the non-linear refractive index, with typical values around -10-10 cm2/W. On the other hand, femtosecond excitation has revealed a pure electronic contribution to the nonlinear refractive index, obtaining values in the order of 10-12 cm2/W. Simulations of heat propagation have shown that the onset of the temperature rise is delayed more than half pulse-width respect to the starting edge of the excitation. A maximum temperature increase of ΔT = 123.1 °C has been found after 3.5 ns of the laser pulse maximum. In order to minimize the thermal contribution to the z-scan transmittance and extract the electronic part, the sample response has been analyzed during the first few nanoseconds. By this method we found a reduction of 20 % in the thermal effects. So that, shorter pulses have to be used to obtain just pure electronic non-linearities.
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A. Martínez, S. Hernández, P. Pellegrino, Y. Lebour, G. Carles, S. Marco, B. Garrido, R. Spano, M. Cazzanelli, N. Daldosso, L. Pavesi, E. Jordana, J. M. Fedeli, "Non-linear optical properties of PECVD Si-nc under nanosecond excitation", Proc. SPIE 6591, Nanotechnology III, 65910A (22 May 2007); doi: 10.1117/12.721955; https://doi.org/10.1117/12.721955
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