22 May 2007 Non-linear optical properties of PECVD Si-nc under nanosecond excitation
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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.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Martínez, A. Martínez, S. Hernández, S. Hernández, P. Pellegrino, P. Pellegrino, Y. Lebour, Y. Lebour, G. Carles, G. Carles, S. Marco, S. Marco, B. Garrido, B. Garrido, R. Spano, R. Spano, M. Cazzanelli, M. Cazzanelli, N. Daldosso, N. Daldosso, L. Pavesi, L. Pavesi, E. Jordana, E. Jordana, J. M. Fedeli, 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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