Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/15211
Title: Nonlinear optical properties of CdS quantum dots
Authors: HE JUN
Keywords: cadmium sulfide nanocrystals, Z-scan technique, exciton, optical switching, two-photon absorption, ultrafast
Issue Date: 4-May-2006
Source: HE JUN (2006-05-04). Nonlinear optical properties of CdS quantum dots. ScholarBank@NUS Repository.
Abstract: Semiconductor nanocrystals (NCs) exhibit strongly size-dependent optical and electrical properties, which is of interest in both fundamental research and optoelectronic applications. In this thesis, nonlinear optical properties are investigated on high quality CdS NCs. Firstly, we have observed size-dependent saturable absorption near the excitonic transition of 1S(e) - 1S3/2(h), which can be described by a third-order and a fifth-order nonlinear process. A two-level model is utilized to explain both irradiance- and wavelength-dependence of the excitonic nonlinearity. Secondly, large and ultrafast off-resonance nonlinearity has been observed in CdS-doped Nafion films with femtosecond Z-scan and pump-probe techniques. The determined figures of merit are close to the target values for all-optical switching devices. Finally, interband two-photon absorption saturation in CdS NCs has been observed, which is qualitatively explained by a state-filling effect and quantitatively described by an inhomogeneously-broadened, saturated two-photon absorption model. These results are quite useful for nonlinear optical devices.
URI: http://scholarbank.nus.edu.sg/handle/10635/15211
Appears in Collections:Ph.D Theses (Open)

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