Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

physica status solidi (a)

Measuring Excitonic Coherence in Nanostructures: Time-Resolved Speckle Analysis versus Four-Wave Mixing

W. Langbein, J. M. Hvam

Published Mar 1, 2000• 7 citations
Publisher

Abstract

The excitonic coherence in semiconductor quantum wells is measured by time-resolved speckle analysis and four-wave mixing. It is found that in the case of single GaAs quantum wells, the results of both methods are in agreement, and can be understood in the framework of an inhomogeneously broadened distribution of localized excitons which are subject to phonon-scattering and radiative recombination. The speckle analysis gives the additional distinction between recombination and pure dephasing processes. In multiple quantum wells, the radiative coupling between the quantum wells leads to a pronounced change of the observed dynamics. In the secondary emission, a strong coherent component with an oscillating time-structure is observed for small scattering angles. This is attributed to the beating of the radiative eigenstates of the stacked structure.

DOI
10.1002/1521-396x(200003)178:1<13::aid-pssa13>3.0.co;2-m

Related papers

Spectral speckle analysis: a new method to measure coherence and dephasing in semiconductor nanostructures

Gerrit Kocherscheidt, W. Langbein, R. Zimmermann

A new method to measure the coherence of inhomogeneously broadened optical excitations in semiconductor nanostructures is presented. The secondary emission of excitons in semiconductor quantum wells is investigated. The spectrally-resolved coherence degree of resonantly-excited light emission is deduced from the intensity fluctuations over the emission directions (speckles). The spectral correlations of the speckles give direct access to the homogeneous line width as function of spectral position within the inhomogeneously broadened ensemble. The combination of static disorder and phonon scattering leads to a partially coherent emission. The temperature dependence of the homogeneous line width is well explained by phonon scattering.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jun 5, 2002•0 citations

Time-Resolved Speckle Analysis: A New Approach to Coherence and Dephasing of Optical Excitations in Solids

W. Langbein, J. M. Hvam, R. Zimmermann

A new method to measure the time-dependent coherence of both homogeneously and inhomogeneously broadened optical excitations in solids is presented. The coherence degree of resonantly excited light emission is deduced from the intensity fluctuations over the emission directions (speckles). This method determines the decays of intensity and coherence separately, thus distinguishing lifetime from pure dephasing. The secondary emission of excitons in semiconductor quantum wells is investigated. Here the combination of static disorder and inelastic scattering leads to a partially coherent emission. The temperature dependence is well explained by phonon scattering.

Physical Review Letters•Feb 1, 1999•123 citations

Ultrafast dynamics of confined and localized excitons in low-dimensional semiconductors

J. M. Hvam, W. Langbein, Paola Borri

Coherent optical spectroscopy in the form of nonlinear transient four-wave mixing (TFWM) and linear resonant Rayleigh scattering (RRS) has been applied to investigate the exciton dynamics of low-dimensional semiconductor heterostructures. The dephasing times of excitons are determined from the decay of the spectrally resolved non- linear signal as a function of the delay between the incident pulses in a two-beam TFWM experiment, and from the real time analysis of single speckles in RRS experiments (pure dephasing). From the density- and temperature- dependence of the dephasing times the exciton-exciton and the exciton-phonon interactions are determined. The degree of coherence of the secondary emission is determined from the speckle analysis.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 24, 1999•0 citations

Spectral speckle analysis of resonant secondary emission from solids

Gerrit Kocherscheidt, W. Langbein, G. Mannarini +1 more

A linear optical method to measure coherence and dephasing of excitations in solids is presented. The spectrally resolved degree of coherence of resonantly scattered light is deduced from the intensity fluctuations over its emission directions (speckles). The spectral intensity correlation gives a direct measure of the dephasing rate within the inhomogeneously broadened ensemble. For localized excitons in semiconductor quantum wells, the combination of static disorder, phonon scattering, and radiative decay leads to a spectral dependence of the emission coherence and the dephasing rate, which is well described by model calculations.

Physical review. B, Condensed matter•Oct 24, 2002•20 citations

Coherent control as a probe of scattering mechanisms in semiconductor quantum structures

X. Marie, Th. Amand, P. Renucci +3 more

Summary form only given. The coherence decay of optically excited electronic systems provides one of the most powerful tools to investigate interaction processes of excited states. In semiconductors, the optical coherence phenomena are usually investigated by nonlinear techniques such as four wave mixing (FWM), photon echo, or reflectivity experiments. Exciton-phonon, exciton-exciton, or exciton-free carriers scattering processes have been explored in recent years with these techniques. As demonstrated recently, a direct measurement of the optical dephasing time can be obtained through the temporal coherent control of electronic excitations. In these experiments, the emission following the excitation by an ultrashort optical pulse sequence, is detected in a non-specular direction (secondary emission). This provides an alternative approach to FWM techniques, which allows us to analyse the scattering processes either with phonons or due to mutual collisions. Using the coherent control technique monitored through the secondary emission (SE), we report on the coherent dynamics of excitons in bare quantum wells (QW) and compare it to that of exciton-polaritons in microcavity (MC) embedded quantum wells.

Quantum Electronics and Laser Science Conference•Jan 20, 2003•0 citations

Excitonic Coherent Emission Process in Semiconductors

Takashi Kuroda

Coherent emission process of excitons in a layered compound GaSe， and in ZnSe/ZnSo．isSeo．s2 multiple quantum wells has been directly observed for the first time， by means of two independent newly-developed methods； time-resolved Brewster-angle reflectance （TRBR） spectroscopy and time-resolved four-wave-mixing （TRFWM） spectroscopy． In TRBR measurement， we have succeeded in observing a distinct free-induction-decay of coherently-driven polarization， with an oscillatory behavior due to finely split exciton levels． An analysis on the basis of a s imple model provides key information on the dynamical phase relaxation process． The result of the TRFWM measurement gives the comprehensive treatment of two dephasing processes； destructive interference due to static inhomogeneous broadening， and dynamical homogeneous phase relaxation． An analysis of TRFWM intensity enables one to exactly determine the homogeneous phase relaxation time． Finally， we show that a comparison between the coherent emission signal measured by TRBR or TRFWM， and third-order nonlinear correlation profile observed by time integrated FWM measurement enables one to make distinction between which of quantum - or classical interference effect causes the beat feature seen in the coherent emission signal．

•Dec 26, 1994•0 citations
The excitonic coherence in semiconductor quantum wells is measured by time-resolved speckle analysis and four-wave mixing. It is found that in the case of single GaAs quantum wells, the results of both methods are in agreement, and can be understood in the framework of an inhomogeneously broadened distribution of localized excitons which are subject to phonon-scattering and radiative recombination. The speckle analysis gives the additional distinction between recombination and pure dephasing processes. In multiple quantum wells, the radiative coupling between the quantum wells leads to a pronounced change of the observed dynamics. In the secondary emission, a strong coherent component with an oscillating time-structure is observed for small scattering angles. This is attributed to the beating of the radiative eigenstates of the stacked structure.
A new method to measure the coherence of inhomogeneously broadened optical excitations in semiconductor nanostructures is presented. The secondary emission of excitons in semiconductor quantum wells is investigated. The spectrally-resolved coherence degree of resonantly-excited light emission is deduced from the intensity fluctuations over the emission directions (speckles). The spectral correlations of the speckles give direct access to the homogeneous line width as function of spectral position within the inhomogeneously broadened ensemble. The combination of static disorder and phonon scattering leads to a partially coherent emission. The temperature dependence of the homogeneous line width is well explained by phonon scattering.
A new method to measure the time-dependent coherence of both homogeneously and inhomogeneously broadened optical excitations in solids is presented. The coherence degree of resonantly excited light emission is deduced from the intensity fluctuations over the emission directions (speckles). This method determines the decays of intensity and coherence separately, thus distinguishing lifetime from pure dephasing. The secondary emission of excitons in semiconductor quantum wells is investigated. Here the combination of static disorder and inelastic scattering leads to a partially coherent emission. The temperature dependence is well explained by phonon scattering.
Coherent optical spectroscopy in the form of nonlinear transient four-wave mixing (TFWM) and linear resonant Rayleigh scattering (RRS) has been applied to investigate the exciton dynamics of low-dimensional semiconductor heterostructures. The dephasing times of excitons are determined from the decay of the spectrally resolved non- linear signal as a function of the delay between the incident pulses in a two-beam TFWM experiment, and from the real time analysis of single speckles in RRS experiments (pure dephasing). From the density- and temperature- dependence of the dephasing times the exciton-exciton and the exciton-phonon interactions are determined. The degree of coherence of the secondary emission is determined from the speckle analysis.
A linear optical method to measure coherence and dephasing of excitations in solids is presented. The spectrally resolved degree of coherence of resonantly scattered light is deduced from the intensity fluctuations over its emission directions (speckles). The spectral intensity correlation gives a direct measure of the dephasing rate within the inhomogeneously broadened ensemble. For localized excitons in semiconductor quantum wells, the combination of static disorder, phonon scattering, and radiative decay leads to a spectral dependence of the emission coherence and the dephasing rate, which is well described by model calculations.
Summary form only given. The coherence decay of optically excited electronic systems provides one of the most powerful tools to investigate interaction processes of excited states. In semiconductors, the optical coherence phenomena are usually investigated by nonlinear techniques such as four wave mixing (FWM), photon echo, or reflectivity experiments. Exciton-phonon, exciton-exciton, or exciton-free carriers scattering processes have been explored in recent years with these techniques. As demonstrated recently, a direct measurement of the optical dephasing time can be obtained through the temporal coherent control of electronic excitations. In these experiments, the emission following the excitation by an ultrashort optical pulse sequence, is detected in a non-specular direction (secondary emission). This provides an alternative approach to FWM techniques, which allows us to analyse the scattering processes either with phonons or due to mutual collisions. Using the coherent control technique monitored through the secondary emission (SE), we report on the coherent dynamics of excitons in bare quantum wells (QW) and compare it to that of exciton-polaritons in microcavity (MC) embedded quantum wells.
Coherent emission process of excitons in a layered compound GaSe， and in ZnSe/ZnSo．isSeo．s2 multiple quantum wells has been directly observed for the first time， by means of two independent newly-developed methods； time-resolved Brewster-angle reflectance （TRBR） spectroscopy and time-resolved four-wave-mixing （TRFWM） spectroscopy． In TRBR measurement， we have succeeded in observing a distinct free-induction-decay of coherently-driven polarization， with an oscillatory behavior due to finely split exciton levels． An analysis on the basis of a s imple model provides key information on the dynamical phase relaxation process． The result of the TRFWM measurement gives the comprehensive treatment of two dephasing processes； destructive interference due to static inhomogeneous broadening， and dynamical homogeneous phase relaxation． An analysis of TRFWM intensity enables one to exactly determine the homogeneous phase relaxation time． Finally， we show that a comparison between the coherent emission signal measured by TRBR or TRFWM， and third-order nonlinear correlation profile observed by time integrated FWM measurement enables one to make distinction between which of quantum - or classical interference effect causes the beat feature seen in the coherent emission signal．