Electronic subband structure in two-dimensional electron gases under intense laser radiations

Effect of a terahertz laser field on the electron-DOS in a GaAs/AlGaAs cylindrical quantum wire: finite well model

“…Indeed, the oscillatory nature of the Bessel functions J 2q (x) leads to the emergence of oscillations in the DOS with the increase (decrease) of the EM field strength (frequency). These features are clear signatures of the DFKE for electrons, as already obtained in 3DEGs (see [12]) and quantum wells [13,16,23].…”

“…The modifications of the laser-driven DOS studied here are strongly dependent on both the laser intensity and the frequency, which suggests a simple optical mechanism for tuning the Fermi level and the density of carriers in each 1D sub-band, with obvious implications for all relevant physical properties, as previously found for quasi-2DEGs irradiated by THz laser fields [16]. For a quantum wire with a fixed number of carriers, a detectable increase in the Fermi energy, with the occupancy of higher (previously empty) 1D sub-bands, is expected as a consequence of the DOS reduction, with direct consequences for the optical and transport properties, a study that is already being developed by the authors.…”

“…This effect is similar to the usual Franz-Keldish effect, which describes the nonvanishing optical absorption below the band-edge followed by characteristic oscillations above the band-edge as a consequence of the application of a uniform electrostatic field [15]. An important consequence of the changes in the DOS mentioned above is the possibility of producing an optical control of the density of the electron gas confined in a modulation-doped semiconductor nanostructure [16], a kind of electronic system in which this quantity plays a central role in the control of both the electron mobility and the conductivity, thus determining its viability for device applications [4]. This control is then important for the design of new optoelectronic devices capable of operating ultrafast modulation and switching of optical signals, with potential applications in optical communications [17][18][19].…”

“…The term 2γ hω = e 2 F 2 0 /(4m * ω 2 ) is the energy of the EM radiation field induced by the DFKE [12,13]. With this time-dependent wavefunction in hands, we adapt Green's function approach introduced by Xu for quasi-2DEGs (see [13,16,22]) to our quasi-1D electronic system 10 . First, note that the complete wavefunction m,n,k z (r, t) = ξ m,n (r, θ ) × χ k z (z, t) is related to the probability amplitude of a process in which one adds an electron in a state |m , n , k z at time t to the system and then it evolves to a state |m, n, k z at time t (>t ), as given by…”

“…Since the DOS marks the maximum number of carriers that can occupy states with energies between ε and ε + dε, governing the optical properties of low-dimensional electronic systems and clearly designating its dimensionality [21], we decided to investigate here in this paper, within a nonperturbative scheme based upon Green's function approach introduced by Xu for treating quasi-2D electronic systems under the action of an in-plane THz radiation field [13,16,22], how the electron-DOS for a cylindrical semiconductor quantum wire is affected by the presence of a nonresonant THz laser field 3 . By taking a GaAs cylindrical wire involved by a coaxial Al x Ga 1−x As layer (x is the AlAs molar fraction) as a prototype, we had to adopt a finite potential well model for correctly computing the discrete energy eigenvalues since this popular pair of semiconductors is known to allow for a significant barrier penetration.…”