Nonlinear optical properties of lens-shaped core/shell quantum dots coupled with a wetting layer: effects of transverse electric field, pressure, and temperature

We report Kerr nonlinearity due to intersubband transitions in a three-level InAs/GaAs dome-shaped quantum dots (QDs) system. The impact of wetting layer and dot size on the electronic, linear and nonlinear optical properties is discussed. The results showed an overall shift of dispersion curves towards lower frequencies, pronounced reshaping of absorption and dispersion curves, and two orders of magnitude enhancement in Kerr nonlinearity due to the presence of a wetting layer.

https://iopscience.iop.org/article/10.1088/2040-8978/16/5/055004/pdf

Kerr nonlinearity due to intersubband transitions in a three-level InAs/GaAs quantum dot: the impact of a wetting layer on dispersion curves

Pressure-induced binding energies of an exciton and a biexciton are studied taking into account the geometrical confinement effect in a CdTe/ZnTe quantum dot. Coulomb interaction energy is obtained using Hartree potential. The energy eigenvalue and wave functions of exciton and the biexciton are obtained using the self-consistent technique. The effective mass approximation and BenDaniel-Duke boundary conditions are used in the self-consistent calculations. The pressure-induced nonlinear optical absorption coefficients for the heavy hole exciton and the biexciton as a function of incident photon energy for CdTe/ZnTe quantum dot are investigated. The optical gain coefficient with the injection current density, in the presence of various hydrostatic pressure values, is studied in a CdTe/ZnTe spherical quantum dot. The pressure-induced threshold optical pump intensity with the dot radius is investigated. The results show that the pressure-induced electronic and optical properties strongly depend on th...

Pressure-induced threshold optical pump intensity in a CdTe/ZnTe quantum dot

Simulation of nonlinear optical and self-focusing effects in AlGaN/GaN spherical quantum dot

In this paper, we theoretically study the effects of the structural dimensions, pressure (P) and temperature (T) on transition lifetime (τ), on the linear (α(1)), nonlinear (α(3) ) and total α absorption coefficients for Tera-Hertz range (1.2–2.88 THz). The structure under investigation consists of two laterally coupled InAs/GaAs lens-shaped quantum dots (LCQDs) connected to a wetting layer. This structure is analyzed by using the Finite Difference Method (FDM) and the effective mass approximation. The analytical expressions of the transition life time, linear, nonlinear and total absorption coefficients are discussed by using the density matrix formalism. Obtained results show that the total absorption coefficient achieves a maximum value in Tera-Hertz range and the resonant peaks shift toward the lower energies (higher) by increasing the pressure (temperature). Also, the transition lifetime decrease (increase) by increasing the temperature (pressure). As well, the spacer width (between quantum dots) effect is well studied and can be controlled and adjusted. This theoretical study gives a new degree of freedom in describing devices based on laterally coupled QDs and on the intra-band transitions of electrons to achieve desired nonlinear optical properties in Tera-Hertz field.

Enhancement of transition lifetime, linear and nonlinear optical properties in laterally coupled lens-shaped quantum dots for Tera-Hertz range

In this study we have performed a numerical approach to investigate the optical properties of GaN/AlN quantum dots (QDs). We have used nice homemade finite element method (FEM) codes to solve the Schrodinger equation, in presence and absence of wetting layer. The optical properties of both well-known, truncated pyramids–shaped, wurtize (WZ) and zinc blande (ZB) QDs have been investigated. It is demonstrated, there is slight amount of difference between all orders of absorption coefficients and relative refractive index changes (RRIC) for both structures. The effect of relaxation rate studied as well. Overlay it is shown that the optical properties ZB/WZ QDs could be engineered in well-manner.

https://www.jeos.org/index.php/jeos_rp/article/download/14011/1165

M. Rezaie

Papers

Linear and nonlinear tunable optical properties of intersubband transitions in GaN/AlN quantum dots in presence and absence of wetting layer