A novel proposal for ultra-high optical nonlinearity in GaN/AlGaN spherical centered defect quantum dot (SCDQD)

In this paper a novel idea for enhancement and tunable optical nonlinearity based on spherical centered defect quantum dot (SCDQD) is proposed. The proposed structure is a special quantum dot including a spherical defect inside it. Complete analysis of the proposed structure based on the effective mass equation is done and optical properties (third-order susceptibilities of quadratic electro-optic effect (QEOE) and third harmonic generation (THG) associated with intersubband transition) of the introduced structure using density matrix method are investigated also. Effects of system parameters including defect and dot on energy levels and optical nonlinearity are examined. We observed that the proposed structure has high nonlinear and tunable susceptibilities suitable for implementation of optical active and passive devices. It is shown that the magnitudes of dipole transition matrix element, third-order susceptibilities of THG and QEOE can be increased significantly compared traditional cases (4.5–10 nm, 10−11–10−9 m2/V2 and 10−12–10−9 m2/V2, respectively). Also, the resonance wavelengths are displaced using these parameters that can be used for realization of tunable devices.