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The Study of Spectra and Nonlinearity of Cdse Qds-Doped Optical Materials

Author: WangChenGe
Tutor: YanJinHua
School: Zhejiang University of Technology
Course: Optics
Keywords: CdSe emission/absorption cross sections quantum dots Z-Scan nonlinear refractive index
CLC: O471.1
Type: Master's thesis
Year: 2013
Downloads: 6
Quote: 0
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Abstract


In recent years, with the development of technology targeting at nanoscaled structure materials, nanoparticles and quantum dots (QDs) come on stage with dazzling shines. The QDs is a sort of semiconductor materials, but the essential difference between the traditional semiconductor materials and QDs is that the energy level structure of the former is continuous while the latter’s is discrete. No doubt the QDs have unique electronic and optical properties due to their unique structure, based on which we can develop much broader fields such as Lasers, sensors, quantum computing devices and so on.The film doping with CdSe/ZnS QDs has been prepared and the emission cross sections of CdSe/ZnS QDs have been obtained by applying the McCumber theory. With the calculated emission cross sections depending on wavelengths the transition lifetime of1.12ns is obtained. By comparison of the calculated lifetime and previously reported ones, we find excellent agreement between the measured and calculated ones. It has been found that the McCumber theory can still be used to calculate the emission cross sections of QDs with discrete energy level structure.After that, the Q-shift CdSe QDs dispersed uniformly in UV glue is fabricated into a thin QDs-doped film. By using single beam Z-Scan apparatus constructed by ourselves under the irradiation of low power continuous wave (CW) produced by DPSS laser with a wavelength of473nm, the optical nonlinear refractive index of Q-shift CdSe QDs-doped film is measured. The results show that the CdSe QDs dispersed in UV glue has a negative nonlinearity and a much larger nonlinear refractive index than other normal materials, of which the order reaches about10-10m2/W. Due to the high nonlinear refractive index of CdSe QDs, we can observe obvious self-defocusing phenomena under the irradiation of low power continuous wave.

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CLC: > Mathematical sciences and chemical > Physics > Semiconductor physics > Semiconductive Theory > Semiconductor quantum theory
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