Complex permittivity of a biased superlattice

Abstract

Intersubband response in a superlattice subjected to a homogeneous electric field (biased superlattice with equipopulated levels) is studied within the tight-binding approximation, taking into account the interplay between homogeneous and inhomogeneous mechanisms of broadening. The complex dielectric permittivity is calculated beyond the Born approximation for a wide spectral region and a low-frequency enhancement of the response is found. A detectable gain below the resonance is obtained for the low-doped GaAs-based biased superlattice in the THz spectral region. Conditions of the stimulated emission regime for metallic and dielectric waveguide structures are discussed. The appearence of a localized THz mode due to BSL placed at the interface vacuumdielectric is described.

Intersubband transitions in a biased superlattice: THz gain and surface mode

“…2 Dielectric permittivity Taking into account the scattering processes exactly we describe the response of BSL by the dielectric permittivity ∆ ⊥ ω written through the spectral density function in the r-th QW [4], A r,ε (x, x ), in the following form [5]:…”