Third-Order Nonlinear Optical Response near the Plasmon Resonance Band of Cu2-x Se Nanocrystals Supported by the National Natural Science Foundation of China under Grant Nos 11274302, 11474276 and 11674240

• Published in: Chinese physics letters 2017-01, Vol.34 (1)
• Main Authors: Zhou, Lan-Qing, Zhang, Yan-Bang, Yan, Teng-Fei, Li, Ying, Jia, Guo-Zhi, Xu, Huai-Zhe, Zhang, Xin-Hui
• Format: Article
• Language: English
• ISSN: 0256-307X
• DOI: 10.1088/0256-307X/34/1/014205

The third-order nonlinear optical properties of water-soluble Cu2-xSe nanocrystals are studied in the near infrared range of 700-980 nm using a femtosecond pulsed laser by the Z-scan technique. It is observed that the nonlinear optical response of Cu2-xSe nanocrystals is sensitively dependent on the excitation wavelength and exhibits the enhanced nonlinearity compared with other selenides such as ZnSe and CdSe. The W-shaped Z-scan trace, a mixture of the reversed saturated absorption and saturated absorption, is observed near the plasmon resonance band of Cu2-xSe nanocrystals, which is attributed to the state-filling of free carriers generated by copper vacancies (self-doping effect) of Cu2-xSe nanocrystals as well as the hot carrier thermal effect upon intense femtosecond laser excitation. The large nonlinear optical response and tunable plasmonic band make Cu2-xSe nanocrystals promising materials for applications in ultra-fast all-optical switching devices as well as nonlinear nanosensors.