Open-system theory of photodetection

The transfer of the statistical properties of the electromagnetic field to the detector signal is reinvesti?ated in terms of the Dicke model with coupling of the photosensitive atoms to a reservoir. The interrelated dynamics of the atomic moments and the field moments as well as the photocounting rate for any initial field state are given in terms of not only the field-atom, but also the atom-reservoir, coupling constants.     

A master equation description of coupled systems. II

Dynamical correlations between two coupled systems are described by means of an infinite hierarchy of equations. The condition for a consistent truncation of the hierarchy is given. It allows to derive a closed equation describing the dynamics of one system. The structure of the equations for the stationary and non-stationary case is discussed and a comparison with other approaches is made.     

Polaritons in confined systems

Polaritons in confined systems are introduced and their dispersion is calculated. The amount of squeezing of confined excitons-polaritons in GaAs quantum wells is evaluated.     

LIDAR multiple scattering from clouds

Multiple-scattering LIDAR return calculations obtained by seven different models for the same specified numerical experiment are compared. This work results from an international joint effort stimulated by the workshop group called MUSCLE for MUltiple SCattering Lidar Experiments. The models include approximations to the radiative-transfer theory, Monte-Carlo calculations, a stochastic model of the process of multiple scattering, and an extension of Mie theory for particles illuminated by direct and scattered light. The model solutions are similar in form but differ by up to a factor of 5 in the strength of the multiple-scattering contributions. Various reasons for the observed differences are explored and their practical significance is discussed.     

Optical properties of microcavity polaritons

This work contains a theoretical analysis of the optical properties of semiconductor quantum wells embedded in planar Fabry-Perot microcavities. In particular, the properties of the system in correspondence to the excitonic transition are studied by means of the polariton formalism. The polariton states in microcavities are derived and the polar-iton dispersion is presented. Particular emphasis is put on the existence of two well distinct regimes depending on the exciton and cavity parameters: strong coupling and weak coupling regime. The main experimental results are reviewed and compared with the prediction of the theory. After the polariton states have been characterized, the optical response of the system is discussed, with particular attention to the photoluminescence measurements. The polariton formation and relaxation through phonon scattering and the effect of the exciton inhomogeneous broadening are considered and, finally, a phe-nomenological model for the polariton photoluminescence spectra is presented.     

Some comments on the use of phased angular momentum states in the theory of coherent spontaneous emission from large systems

We stress the importance of using phased atomic states when describing coherent spontaneous emission from large atomic systems. A sufficient criterion for the existence of a preferred direction of emission is deduced from dynamical arguments.     

Statistical properties of polariton states

Summary The unitary transformation that relates free polarization and photon states to polariton states is constructed. The time evolution of an arbitrary initial state in terms of the polariton Hamiltonian is presented. The many-photon components of polariton states as well as the transition probabilities to polariton states and the intrinsec and time-dependent polariton squeezing are discussed.     

Strongly driven exciton resonances in quantum wells: light-induced dressing versus coulomb scattering

The nonequilibrium dynamics of a two-dimensional electron-hole gas is studied in the regime of strong and resonant pumping of the exciton resonance. The Coulomb collision rates are consistently determined by taking into account the light-induced coherence of the two-band system that leads to a dressing of the carrier spectral functions. The light dressing dramatically reduces the Coulomb scattering efficiency. Results are presented for Rabi oscillations in the time domain and dynamical Stark splitting in the pump-probe absorption spectra.