The three-wave mixing process has been studied as functions of incident photon energy and also of the geometrical configuration when incident photon energy lies around the two-photon resonance of excitonic molecule. Experiments indicate that the intensity of the third order nonlinear light beam is enhanced when the phase matching condition derived from the dispersion of excitonic polariton holds or when incident photon energy is equal to the two-photon resonance of excitonic molecule. The relation between this three-wave mixing process and two-photon resonant Raman scattering so far observed is discussed. It is shown that this three-wave mixing process is regarded as the two-photon resonant, coherent Raman scattering via excitonic molecules.The three-wave mixing process has been studied as functions of incident photon energy and also of the geometrical configuration when incident photon energy lies around the two-photon resonance of excitonic molecule. Experiments indicate that the intensity of the third order nonlinear light beam is enhanced when the phase matching condition derived from the dispersion of excitonic polariton holds or when incident photon energy is equal to the two-photon resonance of excitonic molecule. The relation between this three-wave mixing process and two-photon resonant Raman scattering so far observed is discussed. It is shown that this three-wave mixing process is regarded as the two-photon resonant, coherent Raman scattering via excitonic molecules.

Journal of the Physical Society of JapanDec 1, 198023 citations

Coherent states of excitons

Leonid V. Keldysh

WORLD SCIENTIFIC eBooksNov 1, 20231 citation

Coherent transient in photoluminescence of excitonic molecules in GaAs quantum wells

A. L. Ivanov, Hailin Wang, Jagdeep Shah +4 more

Time-resolved photoluminescence (PL) of excitonic molecules in GaAs quantum wells (QW's) reveals an initial transient characterized by a finite rise and an extremely fast nonexponential decay [H. Wang, J. Shah, and T. C. Damen et al., Solid State Commun. 98, 807 (1996)]. The transient is attributed to coherent quantum evolution towards the molecule ground state of two optically correlated excitons, ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}},$ which undergo the Coulombic attraction. In the present paper, we develop a theory of the transient PL and fit the experimental data. The radiative decay of a quasi-two-dimensional (2D) excitonic molecule is analyzed with the giant oscillator strength model adapted to QW's and with the bipolariton model. Within the 2D bipolariton model, the main ``hidden'' channel of the radiative decay of an excitonic molecule is the resonant dissociation into two outgoing interface (surface) polaritons rather than the observable decay into the bulk radiative modes. We conclude that quasi-2D molecules dissociate already within the initial transient of PL, while the following exponential decay of the molecule-mediated PL is due to the escape of secondary interface polaritons into the bulk modes. According to the 2D bipolariton model, the sequence ``two incoming $\mathrm{photons}\ensuremath{\rightarrow}\mathrm{two}$ virtual $\mathrm{excitons}\ensuremath{\rightarrow}2\mathrm{D}$ $\mathrm{molecule}\ensuremath{\rightarrow}\mathrm{two}$ outgoing interface polaritons'' is a completely coherent process. The fit of the time-resolved molecule-mediated PL provides us with numerical estimates of the exciton-photon coupling in GaAs QW's.Time-resolved photoluminescence (PL) of excitonic molecules in GaAs quantum wells (QW's) reveals an initial transient characterized by a finite rise and an extremely fast nonexponential decay [H. Wang, J. Shah, and T. C. Damen et al., Solid State Commun. 98, 807 (1996)]. The transient is attributed to coherent quantum evolution towards the molecule ground state of two optically correlated excitons, ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}},$ which undergo the Coulombic attraction. In the present paper, we develop a theory of the transient PL and fit the experimental data. The radiative decay of a quasi-two-dimensional (2D) excitonic molecule is analyzed with the giant oscillator strength model adapted to QW's and with the bipolariton model. Within the 2D bipolariton model, the main ``hidden'' channel of the radiative decay of an excitonic molecule is the resonant dissociation into two outgoing interface (surface) polaritons rather than the observable decay into the bulk radiative modes. We conclude that quasi-2D molecules dissociate already within the initial transient of PL, while the following exponential decay of the molecule-mediated PL is due to the escape of secondary interface polaritons into the bulk modes. According to the 2D bipolariton model, the sequence ``two incoming $\mathrm{photons}\ensuremath{\rightarrow}\mathrm{two}$ virtual $\mathrm{excitons}\ensuremath{\rightarrow}2\mathrm{D}$ $\mathrm{molecule}\ensuremath{\rightarrow}\mathrm{two}$ outgoing interface polaritons'' is a completely coherent process. The fit of the time-resolved molecule-mediated PL provides us with numerical estimates of the exciton-photon coupling in GaAs QW's.

Physical review. B, Condensed matterAug 15, 199723 citations

Coherent dynamics of bipolaritons in bulk CdS

Ch. Mann, W. Langbein, U. Woggon +1 more

The coherent dynamics of an optically driven exciton--photon--bipolariton system is studied in bulk CdS. Applying backward-scattering four-wave mixing (FWM) spectroscopy, we analyze the two-photon polarization associated with excitonic molecules and determine the dephasing time ${T}_{2}\ensuremath{\simeq}4.8 \mathrm{ps}.$ We demonstrate that the molecule-mediated FWM signal persists at positive time delays even in the ${\ensuremath{\chi}}^{(3)}$ limit, due to the spatial pinning of coherent polaritons induced by the second pulse. By generalizing the bipolariton model to uniaxial semiconductors, we calculate ${\ensuremath{\tau}}_{\mathrm{rad}}^{\mathrm{XX}}\ensuremath{\simeq}2.8 \mathrm{ps},$ justify the ${T}_{2}{=2T}_{1}$ limit, and prove the bipolariton representation for excitonic molecules in CdS.The coherent dynamics of an optically driven exciton--photon--bipolariton system is studied in bulk CdS. Applying backward-scattering four-wave mixing (FWM) spectroscopy, we analyze the two-photon polarization associated with excitonic molecules and determine the dephasing time ${T}_{2}\ensuremath{\simeq}4.8 \mathrm{ps}.$ We demonstrate that the molecule-mediated FWM signal persists at positive time delays even in the ${\ensuremath{\chi}}^{(3)}$ limit, due to the spatial pinning of coherent polaritons induced by the second pulse. By generalizing the bipolariton model to uniaxial semiconductors, we calculate ${\ensuremath{\tau}}_{\mathrm{rad}}^{\mathrm{XX}}\ensuremath{\simeq}2.8 \mathrm{ps},$ justify the ${T}_{2}{=2T}_{1}$ limit, and prove the bipolariton representation for excitonic molecules in CdS.

Physical review. B, Condensed matterNov 27, 200115 citations

{T}_{2}{=2T}_{1}

limit, and prove the bipolariton representation for excitonic molecules in CdS.