Nonlinear optical response of Ge nanocrystals in silica matrix with excitation of femtosecond pulses |
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Authors: | H.P. Li C.H. Kam Y.L. Lam Y.X. Jie W. Ji A.T.S. Wee C.H.A. Huan |
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Affiliation: | (1) Photonics Laboratory, School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Republic of Singapore, SG;(2) Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore 119260, Republic of Singapore, SG |
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Abstract: | We report an investigation of third-order optical nonlinearities in Ge nanocrystals (∼6 nm radius) embedded in silica matrix using the Z-scan and pump-probe techniques with femtosecond laser pulses at 780-nm wavelength. The nanocrystallite Ge samples were prepared using magnetron co-sputtering and post-thermal annealing at 800 °C. The nonlinear absorption coefficient and refractive index of the Ge nanocrystals were determined to be in the range from 1.8×10-7 to 6.8×10-7 cm/W and 1.5×10-12 to 8.0×10-12 cm2/W, respectively, which are proportional to the Ge atomic fraction in the matrix. Relaxation of the nonlinear response was found to have two characteristic time constants, 1.8 ps and 65 ps. The mechanisms responsible for the observed nonlinear response are discussed. Received: 21 August 2000 / Revised version: 17 January 2001 / Published online: 30 March 2001 |
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Keywords: | PACS: 42.65.An 61.46.+w 78.20.Ci |
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