Propagation of femtosecond pulses in thin ZnSe layers

Abstract

The transmission of optical femtosecond pulses through ZnSe/ZnS,Sel-, heterostructures is investigated in both the spectral and the temporal domain. Quantization of the polariton wave vector within the thin ZnSe layers (23 to 100 nm) leads to a variety of allowed propagating modes which are clearly resolved in transmission spectra. Interference of all contributing modes gives rise to a very pronounced and complex temporal beating behavior of the transmitted pulses measured with femtosecond resolution. The transmission spectra as well as the transients taken from different samples are consistently described by a model based on three-oscillator polariton theory using Pekar's additional boundary conditions.

The 2s exciton in intermediate dimensionality structures

“…They are given by, where V e , and V h are depths of the potential well for the electrons and holes, respectively while E e and E h are the energies of the ground states of the respective particles confined in these quantum wells. It was argued by Mathieu et al [13] that the following expression leads-via the fractional dimension approach-to a satisfactory description of the exciton binding energies observed in GaAs/GaAlAs type-I quantum wells:…”

“…The calculations make use of the energy difference, E 2s − E 1s at 5 T. The experimental uncertainty in measuring this difference is between 0.5 and 1 meV. For E e we have used the value of 21 meV, which is the binding energy of bulk ZnSe [7,13], in the calculations.…”

Mott transition of excitons in ZnSe studied by phase resolved reflection

“…These polariton beats arise due to interference between different polariton waves. Additionally, polariton resonances had been found in the transmission spectrum [4,5], which also could be explained as an effect of spatial dispersion of the interfering polariton modes. Considering spatial dispersion the problem of additional boundary conditions (ABC's) appears which have to be considered in addition to Maxwell's boundary conditions at the interfaces.…”

“…These quasi-particles arise due to coupling of the light field with the semiconductor as dielectric medium [1,2]. The effect of spatial dispersion has been demonstrated in [3][4][5] to be responsible for a beating of the amplitude of the transmitted light within time domain. These polariton beats arise due to interference between different polariton waves.…”

Phase resolved polariton interferences in a ZnSe‐ZnSSe heterostructure

“…Due to spatial dispersion interferences of polariton waves appear, showing up as an additional series of single peaks in the spectrum of transmission/reflection above the exciton resonances [1][2][3][4][5][6]. Fundamental theoretical concepts for the description of polariton propagation were presented in [5,6], based on a strong microscopic, quantum mechanical concept of the calculation of the excitonic polarization in a semiconductor layer.…”