Tunneling Effect And Surface Plasmon Resonances On Nonlinear Optical Properties In Quantum Dots

Because of its unique optical properties and the potential value in optoelectronics,biological medicine,quantum computation and quantum communication etc.,Nonlinear Optics have attracted many researchers in a few decades since it was found.With the nanofabrication technique has obtained great advance in the past few years,it makes possible for us to fabricate the low-dimension semiconductor material.There are three characteristics which make the low-dimension semiconductor material,e.g.,superlattice,quantum well,quantum wire and quantum dot,become a hotspot in the study of the Nonlinear Optics,low power threshold,fast response and the large nonlinear optical coefficients.In all of the low-dimension semiconductor material,the quantum confinement effect in quantum dot is much stronger than in others so that the nonlinear optical effects in quantum dot are also stronger that other low-dimension semiconductor material.With the deeper study of Nonlinear Optics,the nonlinear resonance effect come into researchers' view.Because Surface Plasmon Resonances have a wide range tunable properties which can strengthen the electromagnetic field by focusing the energy of optical field in a nanoscale range so that the study of Surface Plasmon Resonances enhance nonlinear optical properties become a hot topic.For above reasons,we will study the nonlinear optical properties in quantum dot and the enhancement of Surface Plasmon Resonances on nonlinear optical properties in this paper.This article is consisted by five chapters.Chapter one is for introduction and it has three parts.The first part will introduce the basic knowledge and the fabricate method about the low-dimension semiconductor material.The second part will introduce the development,research status and research method of Nonlinear Optics.The third part will introduce the basic knowledge,research status and research method of Surface Plasmon Resonances.In the chapter two,we will study the tunneling effect on second-harmonic generation in quantum dot molecule.Based on the effective-mass approximation,we got the wave function and energy eigenvalues by solving the Schr¨odinger equation of the system.The expression of the second-harmonic generation coefficients can be derived by using the compact-density-matrix approach and iterative method.The numerical results show that the tunneling strength T e and the size of the quantum dot have a great influence on the second-harmonic generation coefficients.In the chapter three,we calculated the dielectric function of gold nanosphere with the influence of Surface Plasmon Resonances.After obtained the quantum corrected dielectric function,we accorded to the Mie theory and used the function to calculate the optical absorption cross section of gold nanosphere.The numerical results show that the size of gold nanosphere has a great influence on its dielectric function and its light absorption cross section.And we can observe the red-shift and the blue-shift in the curves.In the chapter four,by using the quantum corrected dielectric function which we have studied above,we studied the nonlinear optical properties in the semiconductor quantum dot with the influence of Surface Plasmon Resonances.The numerical results show that the center-to-center distance d and the radius ratio h between the metallic nanoparticle and the semiconductor quantum dot have a great influence on the nonlinear optical properties.It is worth to notice that we must consider these two factors when we are doing the theory study and experiment.Chapter five is for the summary and the expectation.We will draw the main conclusions and give the contents of our research.As the same time,the shortage and the flowing work direction will be pointed out in this chapter.