Nonlinear Optical Properties Of Silicon Quantum Dots Embedded Thin Films

The magnitude and property of the nonlinearity in photoelectric materials can determine its application in the nonlinear photoelectric device.In this dissertation, the sample of (nc-Si/SiO₂)/SiO₂ and (nc-Si/a -Si:H)/a -SiNx:H are prepared by using plasma enhanced chemical vapor deposition method. Moreover, we investigate their nonlinear optical properties .Theoretically, with the condition of infinite potential well. we simulate and analyze the third-orde rnonlinear properties of Si quantum dots. Experimentally, On the basis of Z-scan method, we study properties of the nonlinear optical properties of the sample, which is illuminated by continuous laser possessing a wavelength of 532nm. The conclusions are listed as below:1,We do investigate the third-order nonlinear optical properties of the electron in the condition of strong-confinement. It can be found that: The third-order susceptibility will change tremendously when incident photonic energy varies.The third-order susceptibility will increase gradually with the increment of the radium of quantum dot or the decrease of relaxation Phase.2,By the analysis of the third-order nonlinear optical property of exciton both in strong-confinement and weak-confinement, it can be concluded that in the condition of strong-confinement, the smaller does the radium of quantum dot get, the stronger does the third-order optical susceptibility become; In the condition of weak-confinement, the longer does the radium of quantum dot get, the stronger does the third-order optical susceptibility become.and found that the self-focus and defocus are depended on the photon energy and band gap energy.3,From the experimental results, it is found that the nonlinear refractive and nonlinear absorptive effect can be observed clearly in the(nc-Si/SiO2)/ SiO2 and (nc-Si/α-Si:H)/α-SiNx:H samples. The real part of the third-order susceptibility concerning the (nc-Si/SiO2)/SiO2 sample is ? 8.12×10 ?3esu, whilst the imaginary part is 8.77×10 ?4esu.With regard to the (nc-Si/ a -Si:H)/ a -SiNx:H, The real part of the third-order susceptibility is 2.00×10 ?3esu, whilst theimaginary part is ? 5.51×10 ?4esu. The (nc-Si/SiO2)/SiO2 is a self -defocusing media with the property of reverse saturation absorption. The (nc-Si/a -Si:H)/a -SiNx:H is a self-focusing media with the property of saturation absorption. These novel optical property we attribute the quantum confinement and dielectric Confinement effect of materials. (nc-Si/SiO2)/SiO2 will be applied extensively in the field of laser protection and optical limiting devices; (nc-Si/a -Si:H)/a -SiNx:H will be applied in area of the q-switched, mode-locked devices and optical bistable devices.