Numerical analysis of optical properties of oblate semi-spheroid-shaped quantum dots coupled to wetting layer

Abstract

The authors report optical nonlinearity enhancement in oblate semi-spheroid-shaped quantum dots (QDs) coupled to a wetting layer. To reach this result, two groups of InAs/GaAs QDs were examined. In group (A), the base length of semi-spheroid-shaped QDs was set to 14 nm and the height was changed from 3 to 14 nm. In group (B), the height was set to 4 nm and the base length was increased from 10 to 25 nm. The energy eigenvalues, transition energies, transition dipole moments, oscillator strengths, and linear and nonlinear optical susceptibility of the two groups were compared. The nonlinear susceptibility of group (B) QDs was shown to be much more sensitive in both peak position and value to size changes, in contrast to group (A) QDs. Interestingly, a ∼11.4 times increase in real and imaginary parts of the third-order susceptibility was observed when the base length of group (B) QDs was increased from 10 to 25 nm. Moreover, the third-order susceptibility of the most stretched QDs of group (B), i.e., b=25  nm, was shown to be ∼4.6 times larger than the tallest QD of group (A), i.e., h=14  nm. Finally, the figure of merit showed a ∼3.38 times increase with a QD base length increasing from b=10  nm to b=25  nm.