Influence Of Strong Laser Fields And Surface Plasmons On The Nonlinear Optical Properties Of Quantum System

Due to the characteristics of fast response,low threshold power,and significant nonlinear optical coefficients,low-dimensional semiconductor materials have become ideal nonlinear optical materials and are widely used in optoelectronic devices.As the requirements for device accuracy,response speed,and structure size increase,higher demands are placed on the nonlinear optical properties of low-dimensional semiconductor materials.Therefore,low-dimensional semiconductor materials under the action of intense laser field and surface plasmons have become a popular research object today.To investigate the changes of nonlinear optical properties of low-dimensional semiconductor materials under the action of intense laser field and surface plasmons can help to improve the device performance and extend the device function.In this paper,we focus on the effects of intense laser field and surface plasmons on the nonlinear optical properties of quantum systems.After theoretical study,we found some interesting physical phenomena and explained their causes.The research work done in this paper and the main results obtained are as follows:Based on the effective mass approximation,we solve the Schr?dinger equation for the quantum system under the action of the intense laser field using the KramersHenneberger transformation and numerical calculation to obtain the energy levels and wave function distributions of the quantum system under the action of the intense laser field,and find that the intense laser field alters the shape of the quantum wells,which in turn causes the energy levels and wave functions to change.In studying the effect of surface plasmons,we deduce that the coupling between Au nanoparticles and the quantum system causes the energy gap and relaxation rate of the quantum wells to be modified respectively by solving the optical Bloch equation.The analytical expressions for the optical absorption coefficients(OACs)and the optical refractive index changes(ORICs)of the hybrid system consisting of the intense laser field and the quantum wells,the hybrid system consisting of Au nanoparticles and the quantum wells,and the hybrid system consisting of Au nanoparticles and the quantum wells under the action of the intense laser field are derived using the density matrix method and the iterative method.The OACs and the ORICs of the quantum system with different parameters are calculated and discussed.The results show that varying the intense laser field can modulate the peak positions and peak sizes of the OACs and the ORICs of the studied quantum wells,and the shape parameters of the quantum system also have a modulating effect on the OACs and the ORICs.The presence of surface plasmons suppresses the OACs and redshifts the OACs and the ORICs of the studied quantum wells.If Au nanoparticles with a radius of 1 nm and a distance of 2 nm are placed next to the Woods-Saxon quantum wells,a change in barrier gradient parameter of the Woods-Saxon quantum wells hardly affects the peak size of the third-order nonlinear OACs of the system.By studying the effect of surface plasmons on the nonlinear optical properties of the Woods-Saxon quantum wells under the action of the intense laser field,we find that varying the intense laser field can regulate the degree of influence of surface plasmons on the composite quantum system.Therefore,the combined adjustment of the intense laser field,the radius of Au nanoparticles,and the distance between Au nanoparticles and the quantum system can provide a more flexible modulation of the OACs as well as the ORICs.