F. Jahnke

Quantum theory of spontaneous emission and coherent effects in semiconductor microstructures

Abstract A fully quantum-mechanical theory for the interaction of light and electron–hole excitations in semiconductor quantum-well systems is developed. The resulting many-body hierarchy for the correlation functions is truncated using a dynamical decoupling scheme leading to coupled semiconductor luminescence and Bloch equations. For incoherent excitation conditions, the theory is used to describe nonlinear excitonic emission properties of single-quantum wells, optically coupled multiple quantum-well systems, and quantum wells in a microcavity. Resonant coherent optical excitation leads to a direct coupling between the induced coherent polarization and photoluminescence. The resulting quantum corrections to the semiclassical semiconductor Bloch equations and the coherent contributions to the semiconductor luminescence equations are discussed. The secondary emission in directions deviating from the coherent excitation direction after femtosecond-pulse excitation is studied. Coherent control and quadrature squeezing for the light emission are analyzed.

Comparison of experimental and theoretical GaInP quantum well gain spectra

A microscopic analysis of experimental GaInP quantum well gain spectra is presented for a wide range of excitation. A consistent treatment of carrier collision effects, at the level of quantum kinetic theory in the Markovian limit, is found to be necessary for agreement with experiment.

Microscopic theory of gain for an InGaN/AlGaN quantum well laser

This letter describes a microscopic gain theory for an InGaN/AlGaN quantum well laser. The approach, which is based on the semiconductor Bloch equations, with carrier correlations treated at the level of quantum kinetic theory in the Markovian limit, gives a consistent treatment of plasma and excitonic effects, both of which are important under lasing conditions. Inhomogeneous broadening due to spatial variations in quantum well thickness or composition is taken into account by a statistical average of the homogeneously broadened spectra.

Physics of semiconductor microcavity lasers

This review summarizes recent developments and successes in the theoretical modelling of the characteristics of semiconductor microcavity lasers. After a discussion of the basic laser properties, results of a quasi-equilibrium many-body theory are presented which are very useful for the understanding of microcavity laser operation not too far above the laser threshold. Non-equilibrium phenomena, such as spectral and kinetic hole burning as well as plasma heating effects, are analysed using a quantum kinetic approach. Comparisons with experimental observations are discussed, before open problems and future challenges are outlined.

Polariton propagation in high quality semiconductors: Microscopic theory and experiment versus additional boundary conditions

Exciton-polariton propagation in a quantum well, under centre-of-mass quantization, is computed by a variational self-consistent microscopic theory. The Wannier exciton envelope functions basis set is given by the simple analytical model of ref. [1], based on pure states of the centre-of-mass wave vector, free from fitting parameters and ”ad hoc” (the so called additional boundary conditionsABCs) assumptions. In the present paper, the former analytical model is implemented in order to reproduce the centre-of-mass quantization in a large range of quantum well thicknesses (5aB ≤ L ≤ ∞). The role of the dynamical transition layer at the well/barrier interfaces is discussed at variance of the classical Pekar’s dead-layer and ABCs. The Wannier exciton eigenstates are computed, and compared with various theoretical models with different degrees of accuracy. Excitonpolariton transmission spectra in large quantum wells (L ≫ aB) are computed and compared with experimental results of Schneider et al. in high quality GaAs samples. The sound agreement between theory and experiment allows to unambiguously assign the exciton-polariton dips of the transmission spectrum to the pure states of the Wannier exciton center-of-mass quantization.Linear exciton-polariton propagation in semiconductors is analyzed using a microscopic theory. Numerical results are compared with various approximation schemes based on additional boundary conditions, and with phase-amplitude linear spectroscopy experiments in high-quality GaAs. A simultaneous description of the measured amplitude and phase of the transmitted electric field is only possible with the full model.

Theory of carrier heating through injection pumping and lasing in semiconductor microcavity lasers

Nonequilibrium carrier distributions in microcavity lasers are computed by solution of a quantum Boltzmann equation that includes carrier–carrier, carrier–phonon, and carrier–photon scattering as well as the pump process. A significant heating of the carrier plasma is observed as a consequence of the Pauli blocking of carrier injection and the removal of cold carriers through the process of stimulated recombination.

Measurement and calculation of gain spectra for (GaIn)As/(AlGa)As single quantum well lasers

The gain spectrum of a (GaIn)As/(AlGa)As single-quantum-well laser diode is precisely measured at various currents in order to quantitatively check the predictions of a microscopic model. The theory includes carrier—carrier and carrier—LO-phonon collisions which lead to optical dephasing and screening of the Coulomb interaction. The measurements are based on a transmission technique using the broad spectrum of a 10 fs Ti:sapphire laser to obtain sufficient signal to noise ratio over a wide spectral range. We obtain excellent agreement between theoretical and experimental gain spectra and thus can clearly demonstrate the predictive capability of our microscopic model.

Ultrafast intensity switching and nonthermal carrier effects in semiconductor microcavity lasers

A microscopic nonequilibrium theory is applied to investigate the dynamical response of semiconductor microcavity lasers for ultrashort optical pulse excitation. It is predicted that femtosecond pulse induced carrier heating leads to picosecond switching and recovery of the laser emission.

Nonlinear emission dynamics from semiconductor microcavities in the nonperturbative regime

Time-resolved normal-mode-coupling (NMC) oscillations in the nonlinear regime of a semiconductor microcavity with a large splitting to linewidth ratio are studied experimentally using upconversion. A reduction of the modulation depth of the NMC oscillations and reflection dips without a change in the NMC splitting and oscillation period is observed. Microscopic calculations attribute the observed features to excitonic broadening due to dephasing induced by carrier-carrier and polarization scattering processes.

Transient nonequilibrium and many-body effects in semiconductor microcavity lasers

We analyze the dynamical response of the interacting photon and electron–hole system in short-cavity bulk semiconductor lasers, including many-body effects of the electron–hole plasma and photon system, the interaction of electron–hole pairs and photons, and the selection of photon modes by the cavity. Carrier–carrier and carrier-phonon scattering is treated at the level of a quantum Boltzmann equation. Numerical solutions of the coupled equations for spontaneous and stimulated emission and carrier distributions show the development of lasing out of spontaneous emission and the stabilization of laser action connected with gain saturation and spectral hole burning. The saturation of the output intensity and modifications of the relaxation oscillations are investigated.