Anisotropy effect on the nonlinear optical properties of a three-dimensional quantum dot confined at the center of a cylindrical nano-wire

• Published in: Physica. E, Low-dimensional systems & nanostructures Vol. 59; pp. 124 - 132
• Main Authors: Safarpour, Gh, Izadi, M.A., Novzari, M., Niknam, E., Moradi, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2014; Elsevier
• Subjects: Anisotropic quantum dot; Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Materials science; Molecular electronics, nanoelectronics; Nano-wire; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nonlinear optics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Oscillator strength; Physics; Quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Oscillator strength; Nano-wire; Anisotropic quantum dot; Nonlinear optics; Gallium arsenides; Confinement; Quantum dots; Refractive index; Density matrix; Aspect ratio; Absorption coefficients; Spectral line shift; III-V compound; Anisotropy; Optical properties; Oscillator strengths; Eigenvalues; Wave functions; Nanowires; Absorption spectra; Nanostructured materials; Optical absorption; III-V semiconductors
• ISSN: 1386-9477; 1873-1759
• DOI: 10.1016/j.physe.2014.01.007

The effect of geometrical anisotropy is numerically investigated on the linear and nonlinear optical properties of a GaAs quantum dot which is located at the center of a Ga1-xAlxAs cylindrical nano-wire. The finite difference approximation has been used for obtaining energy eigenvalues and corresponding wave functions. Also, the compact density matrix formalism is applied to investigate linear, third order nonlinear and total optical absorption coefficients (ACs) and refractive index (RI) changes. The optical properties and oscillator strength are calculated as a function of the incident photon energy for different ellipsoid aspect ratio, dot radius and incident optical intensity for 1–2, 2–3 and 1–3 transitions. The results clearly reveal that the dot anisotropy plays an important role in determining the magnitude of nonlinear AC and RI changes which enable us to adjust saturation condition. We found that the dot anisotropy shifts absorption spectrum towards both lower and higher energies which depend on the shape of dot (spherical, prolate or oblate quantum dot), dot radius and states between which transitions will occur. Additionally, it is shown that the presence of nano-wire (second confinement) causes (I) a large increment in RI changes (II) a decrement in total AC for prolate QDs with respect to the dot radius (III) an increment in third order AC with respect to the ellipsoid aspect ratio and (IV) a blue shift in optical spectrum. The linear and third order nonlinear optical absorption coefficients and refractive index changes are calculated for an anisotropic QD which is located at the center of a cylindrical nano-wire. [Display omitted] •The nonlinear optical properties of an anisotropic QD are investigated.•The QD is located at the center of a cylindrical nano-wire.•Accuracy of applied method is checked by comparing results with exact eigenvalues.•Blue and red shifts appear in absorption spectrum depending on shape and size of QD.•Refractive index changes are noticeably enhanced by imposing second confinement.