Browsing by Author "Oliveira, L. E."

Now showing 1 - 4 of 4
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    Laser-dressing and magnetic-field effects on shallow-donor impurity states in semiconductor GaAs–Ga1−xAlxAs cylindrical quantum-well wires
    (2010-01) López, F. E.; Reyes Gómez, E.; Porras Montenegro, Nelson; Brandi, H. S.; Oliveira, L. E.
    The influence of an intense laser field on shallow-donor states in cylindrical GaAs–Ga1−xAlxAs quantum-well wires under an external magnetic field applied along the wire axis is theoretically studied. Numerical calculations are performed in the framework of the effective-mass approximation, and the impurity energies corresponding to the ground state and 2p ± excited states are obtained via a variational procedure. The laser-field effects on the shallow-donor states are considered within the extended dressed-atom approach, which allows one to treat the problem 'impurity + heterostructure + laser field + magnetic field' as a renormalized 'impurity + heterostructure + magnetic field' problem, in which the laser effects are taken into account through a renormalization of both the conduction-band effective mass and fundamental semiconductor gap.
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    Laser-dressing effects on the electron g factor in low-dimensional semiconductor systems under applied magnetic fields
    (2009-05) López, F. E.; Reyes Gómez, E.; Brandi, H. S.; Porras Montenegro, Nelson; Oliveira, L. E.
    The effects of a laser field on the conduction-electron effective Landé g factor in GaAs–Ga1−xAlxAs quantum wells and quantum-well wires under applied magnetic fields are studied within the effective-mass approximation. The interaction between the laser field and the semiconductor heterostructure is taken into account via a renormalization of the semiconductor energy gap and conduction-electron effective mass. Calculations are performed for the conduction-electron Landé factor and g-factor anisotropy by considering the non-parabolicity and anisotropy of the conduction band. Theoretical results are obtained as functions of the laser intensity, detuning and geometrical parameters of the low-dimensional semiconductor heterostructures, and indicate the possibility of manipulating and tuning the conduction-electron g factor in heterostructures by changing the detuning and laser-field intensity.
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    Plasmon polaritons in 1D Cantor-like fractal photonic superlattices containing a left-handed material
    (2011-06) Mejía Salazar, Jorge Ricardo; Porras Montenegro, Nelson; Reyes Gómez, E.; Cavalcanti, S. B; Oliveira, L. E.
    The propagation of light incident upon a 1D photonic superlattice consisting of successive stacking of alternate layers of a right-handed nondispersive material and a metamaterial, arranged to form a Cantor-like fractal, is considered. Plasmon-polariton excitations are thoroughly investigated within the transfer-matrix approach and shown to strongly depend on the Cantor step number N. More specifically, the number of plasmon-polariton bands corresponds to the number 2N− 1 of metamaterial layers within the unit cell.
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    Zero-(n) non-Bragg gap plasmon-polariton modes and omni-reflectance in 1D metamaterial photonic superlattices
    (2011-05) Agudelo Arango, C.; Mejía Salazar, Jorge Ricardo; Porras Montenegro, Nelson; Reyes Gómez, E.; Oliveira, L. E.
    A theoretical study of the photonic band structure and transmission spectra for 1D periodic superlattices with an elementary cell composed of two layers of refractive indices n(a) and n(b), which may take on positive as well as negative values, has been performed within the transfer-matrix approach. The dependence on the angle of incidence of the electromagnetic wave for excitation of plasmon-polaritons as well as the properties of the (n) = 0 gap were thoroughly investigated. Results are found for the generalized conditions that must be satisfied by the ratio a/b of the layer widths of metamaterial photonic superlattices, for both transverse electric and transverse magnetic polarizations, in order to have an omnidirectional (n) = 0 gap. The present study indicates new perspectives in the design and development of future optical devices.