Nonlinear optical properties of ZnO thin films measured by Z-scan method

• Main Authors: Yin-Jen Chen, 陳英仁
• Other Authors: Wen-Feng Hsieh
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/18044032509246822269

碩士 === 國立交通大學 === 光電工程系所 === 92 === Optical nonlinearities of ZnO thin film made by the laser MBE have been investigated by Z-scan method from the high repetition rate femtosecond Ti:sapphire laser. The measured positive �� and ���nnear IR shows enormous increasing than the ZnO bulk measured at 532nm with 25ps pulse duration. The two-photon resonance of the bandedge and exciton is observed by the two photon absorption coefficient �� and the free carrier induced nonlinearities with a red shift relative to due to the free carrier saturation. In addition, the linear absorption saturation by the ZnO defect states is observed while the excitation wavelength between 810nm-840nm. By the analysis of thermal-optical effect�z we suggest that the nonlinear refraction index is mainly dominated by the thermal nonlinearity at 420nm. Nevertheless, the bound electronic and free carrier effect is main source of the nonlinear refraction in the near IR range even though the thermal-optical effect can not be neglected.