Linear and Nonlinear Optical Properties of an AlSb/InAs/AlSb Spherical Quantum Dot in a Magnetic Field.

We investigate the optical and electronic properties of a spherical AlSb/InAs/AlSb core/shell/shell quantum dot (QD) under the combined effects of size confinement and an external magnetic field. The system contains a centrally located hydrogenic donor impurity whose attractive Coulomb interaction affects the distribution of electronic energy levels, their corresponding wavefunctions, and their optical responses. The total optical absorption coefficients and refractive index changes are analyzed as functions of incident photon energy by systematically varying the core radius and the applied magnetic field. The results reveal a tunable optical absorption resonance associated with the E1→E2 intersubband transition, whose spectral position and amplitude are strongly modified by the core radius, magnetic-field strength, and presence of the hydrogenic impurity. Increasing the magnetic field intensity from 0 to 30 T redshifts the optical absorption and refractive index peaks by 20-60 meV, reflecting the predominance of magnetic effects in the total confining potential. In contrast, expanding the internal quantum dot radius (core radius) also leads to a redshift, but in a lower-energy range of incident photons (0-20 meV), governed primarily by the quantum-size confinement effect. This net distinction in energy-shift ranges indicates that applying a magnetic field offers a broader tuning mechanism than quantum-size effects in the proposed core/shell/shell QDs. Furthermore, the coexistence of two distinct absorption ranges underscores the potential of AlSb/InAs/AlSb spherical QDs for various technological applications, including multi-band, magnetically tunable infrared and THz-infrared optical photodetectors.