Study On Nonlinear Optical Properties Of Three Quantum Well Systems

The main purpose of this paper is to investigate the influence of quantum wells on nonlinear optical properties.The quantum well formed by position-dependent mass(PDM),semi-exponential quantum wells with polaron effect and short-range bottomless exponential potential well are discussed in three chapters to study on the influence of different nonlinear optical properties.In terms of nonlinear optical properties,the optical absorption coefficient,refractive index change and the third-harmonic generation under the influence of different quantum wells are mainly described in this paper,as well as the reasons for the changes.By solving the Schr?dinger equation of different quantum wells and taking the energy levels and wave functions into the corresponding properties of nonlinear optics,as well as using the parameters,energy intervals,matrix elements and light intensity,the trend of nonlinear optical properties with the effect of special quantum well are mainly analyzed in this paper.After research,this paper mainly draws the following conclusions.Firstly,the influence of position-dependent mass on refractive index changes(RICs)and nonlinear optical absorption(OA)coefficients are theoretically studied,within the framework of the iterative method and the compact-density-matrix approach.Through solving Schr?dinger equation,the eigenfunctions and energy eigenvalues are obtained.The analytic expressions of the OA coefficients and RICs are derived theoretically.The results reveal that the OA coefficients and the RICs are strongly affected by PDM,and both the peaks of them increase when considering PDM.Secondly,nonlinear optical refractive index changes with polaron effects are studied in this Letter.The energy levels and wave functions of the polaron Schr?dinger equation are calculated and brought into the nonlinear RICs to analyze the difference between the effects of the presence and absence of polarons,as well as the specific representation of RICs with polarons.And then,we introduce a short-range bottomless potential which can be exactly integrabled.And the exact solutions of Schr?dinger equation of the potential have been derived through the hypergeometric function.After the results are brought into the system of third-harmonic generation(THG),the special phenomenons of third-harmonic generation under short-range exponential potential with inverse square root singularity will be exhibited,that is,the third-harmonic coefficient(THC)will present a mirror reverse state.At the same time,according to the varied tendency of energy intervals and matrix elements,the energy regions of the third-harmonic coefficient and the value of the THC peaks,as well as thenumbers,are specifically elaborated.