Third-order nonlinear susceptibility in $${\text{CdS/Cd}}_{{x_{1} }} {\text{Zn}}_{{1 - x_{1} }} {\text{S/ ZnS}}$$ CdS/Cd x 1 Zn 1 - x 1 S/ ZnS multilayer spherical quantum dot

In the current work, a nano-scale structure based on spherical quantum dot (QD) is proposed to enhance the third-order nonlinear susceptibility. This nanocomposite contains spherical defect in QD. The effective mass equation is used to calculate the energy levels and Eigen states of the introduced system while the density matrix method is hired to evaluate the optical properties. The structural parameters such as defect and dot influence energy eigenvalues, dipole transition matrix elements and optical nonlinear susceptibility. Our findings have shown that this semiconductor structure has high nonlinear susceptibilities appropriate for application in optical devices. It has been indicated the peaks of QEOE (near w = w0) and TGH (near ω = ω0/3 and ω = ω0) are shifted and their magnitudes are strongly dependent on the core radius, well width and mole fraction. The structure parameters QDs can manage the amplitude and resonance frequency of the nonlinear third-order susceptibilities. Graphical abstract In this work, a nano-scale structure based on spherical quantum dot (QD) is proposed to enhance the third-order nonlinear susceptibilities. This nanocomposite contains spherical defect in QD. Complete analysis of the proposed structure is done based on the effective mass equation and optical nonlinear properties are examined using density matrix method. Effects of structure parameters including defect and dot on energy levels, dipole transition matrix elements (DTMEs) and optical nonlinearity are investigated. The results have shown that the introduced structures have high nonlinear and tunable nonlinear susceptibilities appropriate for application in optical devices. The third-order susceptibilities are increased near two to five orders of magnitudes compared traditional cases.