Influence Of Surface Plasmons Resonance On Nonlinear Optical Properties Of Quantum Dots With Different Shapes

In the light of emergence of lasers,the development of nonlinear optics has made great progress.In 1961,the discovery of double frequency made people pay more attention to nonlinear optics.Today,in just over 50 years,nonlinear optics has achieved great development results in theoretical analysis and experimental research.It has also been widely used in lots of fields and interdisciplinary fields.With the rapid development of nonlinear optics,the resonance nonlinear effect has gradually emerged,making people pay attention to it.Among them,the surface plasmon resonances(SPRs)is the most concerned.When surface plasmon resonances occurs,it will cause local electric field amplification of metal particles.Therefore,SPRs is discussed by many researchers.At the same time,nanotechnology is also booming,and quantum dots of different shapes can be Manufactured.It has been found that the nonlinear optical effects of quantum dots of different shapes of low-dimensional semiconductor nanomaterials are obvious and different.Therefore,this paper theoretically studies the effect of surface plasmon resonance on the nonlinear optical properties of quantum dots with different shapes.In this paper,we first calculate the quantum-corrected dielectric function of metal nanoparticles under the quantum size effect.Then,based on the effect mass approximation,perturbation method,separation variable method and boundary conditions,the energy levels and wave functions of metal nanoparticles,dome shells quantum dots,elliptical quantum dots and triangular quantum dots are derived,respectively.Finally,using the density matrix and iterative method,the analytical expressions of second-order and third-order nonlinear optical properties are numerically calculated,including nonlinear optical rectification coefficient,second harmonic coefficient,third harmonic coefficient,refractive index change and light absorption coefficients analytic expressions.The effects of metal nanoparticle size changes and quantum dot parameter changes on nonlinear optical properties are also discussed.The results show that the enhancement effect of surface plasmons does not change due to the shape change,and the metal nanoparticle size and quantum dot parameters do have a great influence on the nonlinear optical properties.The study found:Firstly,for the research of the optical rectification coefficient and the second harmonic coefficient of the dome quantum dots.When the thickness of the shell layer keep constant,the second harmonic coefficient is first decreased and then increased,but the optical rectification coefficient is monotonously increased.And they all have a red shift.When changing the thickness of the shell,both the light rectification coefficient and the second harmonic generation coefficient appear redshift.Secondly,for the study of the third-order nonlinear optical properties of elliptical quantum dots,the third harmonic coefficient shows a red shift as ? increases.As ? decreases,the third harmonic coefficient,the absorption coefficient,and the refractive index change coefficient will increase.When the radius of the metal nanoparticles increases from 1nm to 2nm,the third harmonic generation coefficient,the light absorption coefficient and the photoinduced refractive index change coefficient are all reduced.Third,for the study of the nonlinear optical properties of triangular quantum dots,as the parameter ? increases,the third harmonic generation coefficient decreases,refractive index change coefficient and absorption coefficient increase.Similar to elliptical quantum dots,when the radius of metal nanoparticles increases from 1 nm to 2 nm,the third harmonic generation coefficient,the light absorption coefficient and the photoinduced refractive index change coefficient all show a decreasing trend.