Open Access Nano Express

Tunable nonlinear optical properties in nanocrystalline Si/SiO2 multilayers under femtosecond excitation

Pei Zhang, Xiaowei Zhang, Jie Xu, Weiwei Mu, Jun Xu*, Wei Li and Kunji Chen

Author Affiliations

National Laboratory of Solid State Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China

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Nanoscale Research Letters 2014, 9:28  doi:10.1186/1556-276X-9-28

Published: 14 January 2014

Abstract

The nonlinear optical properties of nanocrystalline-Si/SiO2 (nc-Si/SiO2) multilayers have been investigated through Z-scan technique by using a Ti-sapphire laser with 50-fs pulse duration at 800 nm as a pump laser. It is interesting to note that with increasing the annealing temperature to make the sample change from amorphous phase to nanocrystalline state, the nonlinear absorption turns the reverse saturation absorption into saturation absorption while the nonlinear optical refraction is also changed simultaneously from self-defocusing to self-focusing. We propose that the localized states at the nc-Si/SiO2 interfaces play the key role in the observed switching behaviors. Our results demonstrate that the tunable optical nonlinearities can be achieved by controlling the microstructures of nc-Si, which can be used as engineering different nonlinear optical devices.