Studies On The Nonlinear Optical Properties In Quantum Well And Quantum Dots

"Strong light optics" or commonly known as”nonlinear optics” is an emerging disci-pline with laser technology development.It focuses on the emergence of laser technology,people Through the process of a strong coherent interaction with matter, a variety of newphenomena and new efects, Including these new phenomena, new efects arising from thecauses and course of regular in-depth understanding, as well as to explore their currentor future science and technology development in a variety of possible applications. Sci-ence and technology have been developing rapidly in the world today. Creative abilityof science and technology has become a region, a world, especially a nation of economicand social development of the core competitive power. In many Complexity of the areaof technology, the development of the optical and photonics directly afect other areas ofdevelopment and the subject may be achieved. Not only physics, chemistry, astronomy,and life science And other basic science can’t develop without optical and photonics, themodern human society and the infuence of the human life is great some technology ofscience such as lighting, communications, clean energy, remote sensing, display, Envi-ronmental monitoring national defense and space development, medical treatment anddiagnosis, advanced manufacturing, and need optical and photonics knowledge. Opticaland photonics is to penetrate to each subject area within the frontier science, Optical andphotonics involved almost all the core technology of the technological edge. So that thenonlinear optical in many high technology felds have also been widely used, Such as lasertechnology, optical coherence frequency conversion, ultrashort optical pulse technology,high points become spectrum technique, high rate long distance optical fber communi-cation, light information processing and storage technology, optical communication andelectronic technology, etc.The frst chapter is introduction. First, we mainly introduces the research felds anddevelopment process of the nonlinear optics. secondly, we mainly introduces the maincontents, and the last part we mainly introduced the theory research methods used.In the second chapter, polaron efects on the third-harmonic generations coefcientin cylindrical quantum dots with applied electric feld is theoretically investigated. Inthe efective mass approximation, we lay out the expression of the wave function and theenergy levels of this system. The analytical expression of the third-harmonic generationcoefcient is obtained by using the compact density-matrix approach and the iterativemethod. We also use GaAs/AlGaAs to fnd out how the third-harmonic generations. The results show that the electron-phonon interaction in GaAs/AlGaAs quantum dotsincreases the third-harmonic generations with up to a factor of3. In addition，we fndthat the third-harmonic generations coefcient is related to the parabolic confnementfrequency、the applied electric feld F、the radius of cylindrical quantum dots and theralaxation times.In the third chapter, Polaron efects on the optical absorption coefcients and refrac-tive index changes in a square quantum well is studied. under efective-mass approxima-tion, we solve the Schr¨odinger equation to get the expressions of the wave functions andthe energy levels of this system. The corrections of polaron efects on the wave functionsand on the energies are both considered. The expressions of the optical absorption co-efcients and refractive index changes are obtained by using the compact density-matrixapproach and the iterative method. We fnd that the polaron efect has an importantinfuence on the linear, third-order nonlinear, and total absorption coefcients as well asthe refractive index changes.In the fourth chapter, Polaron efects on the refractive index changes in cylindricalquantum dots with parabolic potential is theoretically investigated. The analytic ex-pression of the refractive index changes are derived by using the compact-density-matrixapproach and iterative method and the expressions of the wave functions and on the ener-gies are obtained by perturbation theory. When we consider the polaron efects, the linear,third-order nonlinear, and the total refractive index changes obtained with consideringelectron-LO-phonon interaction is stronger than the one without considering electron-LO-phonon interaction. The results show that it is distinct for the polaron efects on therefractive index changes. In conclusion the electron-phonon interaction efect can not beignored in studying the optical characters of the low dimensional quantum structure.In the last chapter, the main contents and conclusions of this thesis have been sum-marized.