Microscopic Theory of the Time-Dependent Optical Response from Quantum Wells

Abstract

The reflected and transmitted energy flux corresponding to the linear response of a quantum well (QW) is calculated analytically for the cases of monochromatic and pulsed incident radiation normal to the QW plane. The light–matter interaction has been taken to all orders of perturbation theory, resulting in the appearance of radiative broadening in the expressions for the secondary fields. Three time scales determine the decay of the response after the pulse excitation while the quantum beats are superimposed on the exponentially decaying contributions at the frequency which (i) equals detuning from the electronic transition or (ii) corresponds to a characteristic excitation in the system.

Change in the shape of a symmetric light pulse passing through a quantum well

“…In [1,10,11] the strongly asymmetrical pulse has been used with a sharp front, for which γ l2 → ∞ and the second term in Eq. (5) vanishes, as well as the second term in the square brackets in Eq.…”

“…Therefore the results obtained above are justified for any number of the excited energy levels in a QW (see for instance [10,11,12,13,14]), but not only in the case of the only energy level, where the expression Eq. (15) is applicable.…”

“…In the perfect QWs the radiative lifetime broadening γ r may be comparable to and even exceed the contributions of other relaxation mechanisms. This new physical situation requires the adequate theoretical description where the upper orders of the electron-EMF (electro magnetic field) are taken into account [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. γ r has been calculated for an excitonic energy level in a QW at H = 0 in [2], in a strong magnetic field in [11,12], for a magnetopolaron in a QW in [12], respectively.…”

Microscopic theory of exciton coherent control and Rayleigh scattering in semiconductor quantum wells

“…This is exactly the type of state which describes a coherent electromagnetic field such as that of a laser far above the threshold [27]. (iii) Each excitonic mode, (0 || , α, M), is fully characterized by a single complex function K 0||,α,M (t), which depends on the applied external field (see (14)).…”

Control of Electron Coherences with Coherent Phonons

“…Each possibility is related to a different kind of theoretical picture. The first one relies on the classical picture in which an electric dipole linearly proportional to the exciting electric field of the laser is induced in the QW, considered as a dielectric [73][74]. The induced macroscopic dipole emits radiation that decays in a typical time T 2 (usually much shorter than tie radiative decay time 7V The second possibility brings us to a microscopic picture in which the laser creates a quantum coherent superposition state of excitons that decays in the time T%.…”