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Polaron Effects on Nonlinear Optical Properties of a Hydrogenic Impurity in a CdTe/ZnTe Quantum Dot

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Azhagu Parvathi A., John Peter A.

Acta Physica Polonica A

2013

vol. 124

issue 4

706-712

Hydrogenic donor impurity binding energy is obtained in a Zn_{x}Cd_{1-x}Te/ZnTe strained quantum dot taking into account the phonon confinement effect. The interaction of the electron and the phonon modes are expressed in terms of the Fröhlich interaction Hamiltonian. The binding energy is obtained for various Zn composition using the Aldrich-Bajaj effective potential. Calculations have been obtained using the Bessel function as an orthonormal basis for different confinement potentials of barrier height considering the internal electric field induced by the spontaneous and piezoelectric polarizations. Polaron induced linear and third-order nonlinear optical absorption coefficients and the changes of refractive index as a function of incident photon energy are observed. Our results coincide with the recent observations of a hydrogenic impurity binding energy in a CdTe/ZnTe quantum dot solved analytically. It is observed that the potential taking into account the effects of phonon makes the hydrogenic binding energies larger than the obtained results using a Coulomb potential screened by a static dielectric constant and the optical properties of hydrogenic impurity in a quantum dot are strongly affected by the confining potential and the quantum size. It is found that the geometry of the quantum dot, zinc concentration and the effect of phonon have a great influence on the absorption coefficient and refractive index changes of the dot. It is also observed that the magnitude of the absorption coefficients enhances with the inclusion of phonon effect.

Impurity-Related Linear and Nonlinear Optical Absorption Coefficients of Unstrained (In,Ga)N-GaN Symmetric Coupled QWs

100%

El Ghazi H., John Peter A.

Acta Physica Polonica A

2015

vol. 127

issue 3

787-790

Linear, third-order nonlinear and total optical absorption coefficients associated with intra-conduction band in wurtzite unstrained (In,Ga)N-GaN coupled quantum wells are calculated. Based on the effective-mass and the one-band parabolic approximations, the well and the barrier-widths effects are investigated variationally under finite confinement potential barrier. The results indicate that the structure size have a great influence on the optical properties. The results reveal also that larger optical absorption coefficients are obtained compared to single quantum well and a significant red-shift is obtained as the structure size increases. It is found that the modulation of the absorption coefficients can be easily obtained by adjusting the barrier and/or the well widths.

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2 Acta Physica Polonica A

1 2015

1 2013

2 John Peter A.

1 Azhagu Parvathi A.

1 El Ghazi H.

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Polaron Effects on Nonlinear Optical Properties of a Hydrogenic Impurity in a CdTe/ZnTe Quantum Dot

Impurity-Related Linear and Nonlinear Optical Absorption Coefficients of Unstrained (In,Ga)N-GaN Symmetric Coupled QWs