We consider the influence of intense coherent laser fields on electronic and optical properties semiconductors. Using nonequilibrium Green's-function techniques exploiting analogies to superconducting Bose-condensed systems, we discuss nature renormalizations collective excitations in collisionless regime. Experimentally, this situation can be realized (i) under nonresonant excitation virtual electron-hole pairs (ii) resonant with ultrashort pulses. explain recently observed Stark effect as...

Absorption, gain, and luminescence spectra of quasi-two-dimensional electron-hole plasmas in semiconductor quantum-well structures are calculated as functions the plasma density temperature. Self-energy corrections effects multiple scattering evaluated for a statically screened Coulomb interaction. The Bethe-Salpeter equation pair propagator is solved both numerically analytically using method developed by Noyes. resulting deviate considerably from corresponding free-particle spectra, due to...

We have investigated the band-gap renormalization due to many-body effects in electron-hole plasmas 2D GaAS-GaAlAs multiple quantum-well structures. A comparison of these data with corresponding 3D and calculations for both dimensionalities shows that shift increases absolutely but decreases effective Rydberg units decreasing dimensionality. The dimensionality dependence is traced different screening efficiencies systems.

The main mechanisms for the observed large optical nonlinearities in semiconductors are briefly discussed and illustrated example of exciton ionization by plasma screening. These cause various types bistability, either intrinsic nature or evoked an additional resonator feedback. Under certain operation conditions also higher instabilities such as oscillations chaos can be obtained. As example, self-pulsing induced absorber a ring cavity is treated. resulting locked shown to follow Farey-tree...

Oscillations of the transient four-wave-mixing signal with a period about $100\mathrm{fs}$ are observed in bulk GaAs using 14 fs pulses tuned to exciton resonance at low temperatures. The measurements explained terms non-Markovian quantum kinetics for electron-hole pairs due LO-phonon scattering. It is shown that oscillations evidence memory effects. experiments provide first test central ideas kinetics, which effects coherence and dissipation intrinsically connected.

Quantum-mechanical rate equations are derived for semiconductor lasers (SL). Fluctuation operators with shot-noise character describe the quantum nature of transitions. These treated in high-temperature limit pure and highly doped III-V compound semiconductors. Numerical calculations carried out GaAs. From mean we determine (a) temperature dependence threshold pump bulk SL current junctions (b) dependences light intensity quasi-Fermi-level. By linearizing fluctuations around values, noise...

Semiconductors are known to show in the band-gap region relative large changes of their optical properties with increasing light intensity. These due creation electron–hole pairs, which modify by band filling intraband and interband contributions complex dielectric function. Most important, concentration gap shrinks, Coulomb forces strongly reduced so that excitonic effects disappear. The theoretical description these phenomena three- quasi-two-dimensional semiconductors is reviewed.

We have analyzed the dependence of band-gap renormalization due to many-body effects on carrier density in electron-hole plasmas quasi-two-dimensional systems. A comparison data obtained at low lattice temperatures various $\mathrm{GaAs}/{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$, GaSb/AlSb, and ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}/\mathrm{InP}$ multiple-quantum-well structures shows that shift, if scaled effective excitonic units, is independent...

Abstract The gain spectrum of a degenerate electron–hole plasma for direct gap semiconductors is calculated as function the density and temperature electronic excitations. calculation contains collision broadening in single‐particle self‐energies excitonic enhancement due to attractive interaction plasma. For example GaAs numerically shown fit experimentally determined spectrum.

Abstract The intrinsic recombination processes are investigated in highly excited II–VI compound semiconductors which involve the following scattering processes: exciton‐exciton (P 2 line), exciton‐electron or ‐hole scattering, and sattering of an exciton by emission a longitudinal optical phonon. From stationary rate equations laser threshold maxima spontaneous stimulated for various determined. Experimental investigations these carried out CdS platelets, ZnO ZnTe crystals. Good agreement...

We study the Coulomb quantum kinetics of relaxation and dephasing an electron-hole gas in a semiconductor excited by coherent femtosecond laser pulse. Our theory employs full two-time-dependent RPA-screened potential. The self-consistently calculated potential evolves from bare to well-known dynamically screened RPA for long times. time dependence particle distributions, interband polarization, are calculated. As first application we Rabi flopping with resonant pulses.

Abstract Nonequilibrium Green's function theory is employed to derive with the use generalized Kadanoff‐Baym ansatz quantum kinetic equations for interband polarization and densities of electrons holes. These are valid in regime ultrafast spectroscopy, where that usual Boltzmann kinetics its individual energy‐conserving collisions no longer holds. The memory kernel retarded determined by advanced functions. It stressed explicitly shown numerical solutions an adjacent paper these functions...

Quasi-equilibrium relaxational thermodynamics is developed to understand LA-phonon-assisted thermalization of Bose-Einstein distributed excitons in quantum wells. We study the quantum-statistical effects dynamics effective temperature $T = T(t)$. When $T$ less than degeneracy $T_0$, well-developed statistics well leads nonexponential and density-dependent thermalization. At low bath temperatures $T_b \to 0$ quantum-statistically degenerate effectively slows down $T(t) \propto 1 / \ln t$....

The ultrafast transition of an optical phonon resonance to a coupled phonon-plasmon system is studied. After 10-fs photoexcitation i-InP, the buildup coherent beats emerging hybrid modes directly monitored via ultrabroadband THz spectroscopy. anticrossing mapped out as function time and density. A quantum kinetic theory microscopic carrier-carrier carrier-LO-phonon interactions explains delayed formation collective modes. quantitatively reproduced scale with oscillation cycle upper branch resonance.

Band-edge absorption spectra for a probe beam under the action of nonresonant pump are calculated and analyzed within Hartree-Fock theory. As result many-body interactions, one obtains an exciton optical Stark shift with constant (2D) or slightly increasing (3D) oscillator strength in agreement several recent experiments striking contrast to corresponding atomic observations. Apparently, deviating results earlier semiconductor were partly caused by dynamical effects presence real excitations.

The fusion of two excited polaritons into an excitonic molecule gives rise to intensity dependence the dielectric function. use this nonlinearity obtain optical bistability with platelets direct-band-gap semiconductors is suggested.