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Excitonic effects on the second-order nonlinear optical properties of semi-spherical quantum dots.

Flórez J, Camacho A - Nanoscale Res Lett (2011)

Bottom Line: The exciton is confined in a semi-spherical geometry by means of a three-dimensional semi-parabolic potential.We calculate the optical rectification and second harmonic generation coefficients for two different values of the confinement frequency based on the numerically computed energies and wavefunctions of the exciton.We find that the second-order nonlinear coefficients exhibit not only a blue-shift of the order of meV but also a change of intensity compared with the results obtained ignoring the Coulomb interaction in the so-called strong-confinement limit.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física, Universidad de los Andes, A,A, 4976, Bogotá, DC, Colombia. j.florez34@uniandes.edu.co.

ABSTRACT
We study the excitonic effects on the second-order nonlinear optical properties of semi-spherical quantum dots considering, on the same footing, the confinement potential of the electron-hole pair and the Coulomb interaction between them. The exciton is confined in a semi-spherical geometry by means of a three-dimensional semi-parabolic potential. We calculate the optical rectification and second harmonic generation coefficients for two different values of the confinement frequency based on the numerically computed energies and wavefunctions of the exciton. We present the results as a function of the incident photon energy for GaAs/AlGaAs quantum dots ranging from few nanometers to tens of nanometers. We find that the second-order nonlinear coefficients exhibit not only a blue-shift of the order of meV but also a change of intensity compared with the results obtained ignoring the Coulomb interaction in the so-called strong-confinement limit.

No MeSH data available.


Related in: MedlinePlus

Characteristic (a) lengths and (b) energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency. The red (black) lines correspond to L and ħω0 ( and ), respectively.
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Figure 1: Characteristic (a) lengths and (b) energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency. The red (black) lines correspond to L and ħω0 ( and ), respectively.

Mentions: In Figure 1, we plot the characteristic lengths and energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency ω0. and are independent on ω0 because they are related to the Coulomb potential. In Figure 1a, we can see that the lengths L and are of the same order of magnitude for a confinement frequency around ω0 = 1 × 1013 s-1. In Figure 1b, we observe that also ħω0 and show similar values around ω0 = 1 × 1013 s-1. For this reason, we conclude that, in this frequency range, neither the strong-confinement limit nor the weak limit can be assumed because both interactions, harmonic and Coulomb, are important. Therefore, we propose a numerical technique to calculate eigenenergies and eigenstates of Hamiltonian (8), considering the harmonic and Coulomb potentials.


Excitonic effects on the second-order nonlinear optical properties of semi-spherical quantum dots.

Flórez J, Camacho A - Nanoscale Res Lett (2011)

Characteristic (a) lengths and (b) energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency. The red (black) lines correspond to L and ħω0 ( and ), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211331&req=5

Figure 1: Characteristic (a) lengths and (b) energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency. The red (black) lines correspond to L and ħω0 ( and ), respectively.
Mentions: In Figure 1, we plot the characteristic lengths and energies for the confined particle in a GaAs/AlGaAs quantum dot as a function of the confinement frequency ω0. and are independent on ω0 because they are related to the Coulomb potential. In Figure 1a, we can see that the lengths L and are of the same order of magnitude for a confinement frequency around ω0 = 1 × 1013 s-1. In Figure 1b, we observe that also ħω0 and show similar values around ω0 = 1 × 1013 s-1. For this reason, we conclude that, in this frequency range, neither the strong-confinement limit nor the weak limit can be assumed because both interactions, harmonic and Coulomb, are important. Therefore, we propose a numerical technique to calculate eigenenergies and eigenstates of Hamiltonian (8), considering the harmonic and Coulomb potentials.

Bottom Line: The exciton is confined in a semi-spherical geometry by means of a three-dimensional semi-parabolic potential.We calculate the optical rectification and second harmonic generation coefficients for two different values of the confinement frequency based on the numerically computed energies and wavefunctions of the exciton.We find that the second-order nonlinear coefficients exhibit not only a blue-shift of the order of meV but also a change of intensity compared with the results obtained ignoring the Coulomb interaction in the so-called strong-confinement limit.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física, Universidad de los Andes, A,A, 4976, Bogotá, DC, Colombia. j.florez34@uniandes.edu.co.

ABSTRACT
We study the excitonic effects on the second-order nonlinear optical properties of semi-spherical quantum dots considering, on the same footing, the confinement potential of the electron-hole pair and the Coulomb interaction between them. The exciton is confined in a semi-spherical geometry by means of a three-dimensional semi-parabolic potential. We calculate the optical rectification and second harmonic generation coefficients for two different values of the confinement frequency based on the numerically computed energies and wavefunctions of the exciton. We present the results as a function of the incident photon energy for GaAs/AlGaAs quantum dots ranging from few nanometers to tens of nanometers. We find that the second-order nonlinear coefficients exhibit not only a blue-shift of the order of meV but also a change of intensity compared with the results obtained ignoring the Coulomb interaction in the so-called strong-confinement limit.

No MeSH data available.


Related in: MedlinePlus