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Journal of Physics Condensed Matter

Excitonic effects on the third-harmonic generation in parabolic quantum dots

Guanghui Wang, Kangxian Guo

Published Aug 16, 2001• 110 citations
Publisher

Abstract

Excitonic effects on the third-harmonic-generation coefficient for disclike parabolic quantum dots are studied, and an analytic formula for the third-harmonic-generation coefficient is obtained by using the compact-density-matrix approach and an iterative method. Numerical results are presented for typical GaAs/AlGaAs parabolic quantum dots. The results show that the third-harmonic-generation coefficient is greatly enhanced because the excitons are localized in the quantum dots - it is over three times that obtained by just considering electron states - and that it is very sensitively dependent on the exciton confinement. In addition, the third-harmonic-generation coefficient is related to the relaxation constant.

DOI
10.1088/0953-8984/13/35/324

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The linear and the third-order nonlinear optical properties of an exciton confined in a three-dimensional quantum dot with a parabolic potential are studied in a static magnetic field. Eigenvalues, wave functions, dipole matrix elements and selection rules are calculated analytically. Based on the calculated energies and wave functions, within the effective mass approximation, a compact-density matrix approach is employed to analyse the absorption coefficients and refractive index changes. The study is first of its kind since the excitonic effects are studied in a static magnetic field considering both the confinement potential and the electrostatic interaction between the electron-hole pair. An important finding of our research is the dependence of the magnitude of absorption coefficients on the radius of the quantum dot, the result that may have broad implications in future device designing.
Abstrcat The linear and nonlinear susceptibilities had been obtained by the compact-density-matrix approach in presence of the multifrequency incident optical field. An analytic formula for third-harmonic-generation was presented by graphic technology(Feynman). Numerical results were presented for typical GaAs/AlGaAs Morse quantum well. The results showed that third-harmonic-generation increased with the enhancement of a and decreased with relaxation constant increasing. Therefore, if the parameter was increased or the relaxation constant was reduced with the effects on the system associated by environment and other factors limited to minimum,a large third-harmonic-generation coefficient would be obtained.