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Nonlinear optical rectification and electronic structure in asymmetric coupled quantum wires
摘要： Asymmetric coupled quantum wires provide the possibility for realizing obvious nonlinear optical rectification due to breaking the inversion symmetry. Here, we investigated nonlinear optical rectification (NOR) and electronic states in asymmetric coupled quantum wires (ACQWs). We find that the NOR max value of the ACQWs exhibits double peak structure with the increase of the geometrical asymmetry (i.e. the left wire radius deviating from the right wire radius), thus offering a direction for achieving remarkable NORS. In the double peak structure, the max value is one to two orders of magnitude larger than the min value. Furthermore, we find that the tunneling effect with respect to the ground state is reduced with the increase of the geometrical asymmetry, while the tunneling effect with respect to the first-excited state is firstly reduced, subsequently enhanced and then reduced with the increase of the geometrical asymmetry. Such coupling pictures elucidate the double peak structure in the NOR max value of the ACQWs. Our work enriches our understanding for the NOR and quantum states of the ACQWs, thereby laying the groundwork for the design and optimization of nonlinear nano-optical devices based on asymmetric coupled quantum wires such as THz radiation sources and infrared photo-detectors.
关键词： Asymmetric coupled quantum wires,Electronic structure,Nonlinear optical rectification
更新于2025-09-23 15:19:57
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Oscillatory behaviour in the energy and nonlinear optical rectification spectra of elliptic quantum rings under electric field: influence of impurity and eccentricity
摘要： We have theoretically investigated the electronic properties and nonlinear optical rectification spectra of GaAs/AlGaAs anisotropic quantum ring, modelled by an outer ellipsis and an inner circle, in connection to the presence of a donor off-centre impurity, structural distortions and in-plane electric field. The one-electron energy spectrum and wave functions are found using the adiabatic approximation and the finite element method within the effective-mass model. The energy spectrum of the ring reveals an anomalous oscillatory behaviour in the region of relatively small values of the electric field (< 12 kV/cm) followed by linear Stark effect at higher field values. We showed that this unusual behaviour is strongly affected by the ratio of the outer/inner ring radii, the displacement of the inner circle (eccentricity) along the x or y axis and the impurity presence. The related nonlinear optical rectification spectra present maxima whose positions mirror this oscillatory behaviour and consequently can be used as an excellent tool to distinguish the presence of an impurity or the direction of the eccentricity.
关键词： nonlinear optical rectification,eccentricity,Quantum ring,donor impurity,electric field
更新于2025-09-09 09:28:46