Spectral features and optical absorption of vertically stacked V-groove quantum wires

Abstract

The spectral features and the linear, nonlinear, and total optical absorption coefficients of two realistic mathrm {GaAs/Ga}_{1-x}{mathrm{Al}}_x{mathrm{As}} vertically stacked V-groove quantum wires confining electronic states were theoretically studied. The compact density matrix formalism and the finite element method were used as solution frameworks. The influence of the barrier width, inter-sidewall angle, the crescent thickness of the stack, and the influence of a static electric field on the energy spectrum and the optical coefficients is addressed. Increasing the crescent thickness (inter-sidewall angle) leads to a reduction (non-monotonous increase) of the energy values, while the presence of a static electric field leads to controllable stark-like patterns. In all cases, anti-crossing points are reported. By increasing the crescent thickness, inter-sidewall angle, or barrier width, a non-monotonous blue-/red-shift of the resonant peaks of the optical absorption is observed. In addition, the results in asymmetric/symmetric vertically coupled V-groove quantum wire systems suggest that the quantum tunneling phenomenon can be linked to the enhancement of the total optical absorption due to the possibility of the generation of dipole moments by higher electron mobility. Thus, optical fields oriented along the growth direction enhance the optical absorption. Furthermore, the absorption coefficient maximum is drastically modified by varying the inter-sidewall angle, and even the evolution tendency can be inverted due to the anti-crossing points in the energy spectra. Since the obtained resonant peaks are located below 20 meV in the spectra, the analyzed system could be interesting for exploring and designing new Terahertz devices.