標題: Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films
作者: Lin, JH
Chen, YJ
Lin, HY
Hsieh, WF
光電工程學系
Department of Photonics
公開日期: 1-Feb-2005
摘要: Optical nonlinearities of ZnO thin films, made by laser deposition, were investigated by the Z-scan method using a mode-locked femtosecond Ti:sapphire laser. The measured bound-electron nonlinear index of refraction gamma and the two-photon absorption coefficient beta at near-IR wavelengths show an enormous enhancement compared with measurements on bulk ZnO at 532 nm. The results reveal that two-photon resonance to the band edge and exciton energy level is responsible for the nonlinear absorption and that the free carrier induced the optical nonlinearity. With the excitation wavelength operated between 810 to 840 nm, a negative beta value is measured due to the saturation of linear absorption of the defect states. Finally, we compared the values of beta from the closed aperture Z-scan data (by considering the multi-photon absorption induced thermal nonlinearity) with those obtained from the open aperture Z-scan data. The results show that nonlinear refraction in the near-IR region is dominated by the bound-electron and free-carrier effect, although the thermal optical nonlinearity cannot be completely ignored. (C) 2005 American Institute of Physics.
URI: http://dx.doi.org/10.1063/1.1848192
http://hdl.handle.net/11536/14014
ISSN: 0021-8979
DOI: 10.1063/1.1848192
期刊: JOURNAL OF APPLIED PHYSICS
Volume: 97
Issue: 3
結束頁: 
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