A. Girndt

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.

Carrier correlation effects in a quantum-well semiconductor laser medium

This paper describes the results of a microscopic treatment of carrier-carrier scattering effects in the optical gain and refractive index spectra of a quantum-well semiconductor laser structure. The approach uses the Semiconductor Maxwell Bloch equations to describe the interaction between the carriers and the laser field, in the presence of many-body Coulomb interactions. Coulomb correlation effects are treated at the level of quantum kinetic theory in the Markovian limit. This approach shows the presence of nondiagonal Coulomb correlation contributions, in addition to the familiar diagonal contributions giving rise to polarization dephasing.

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.

Theoretical analysis of ultrafast pump-probe experiments in semiconductor amplifiers

Pump‐probe experiments in semiconductor amplifiers are analyzed theoretically. On the basis of Maxwell–Semiconductor–Bloch equations it is shown that the probe signal exhibits dominant oscillatory interference‐like structures. These structures are superimposed on the pump and probe intensity dependent features. The calculations are qualitatively similar to experimental results.

Gain Spectra of an (InGa)As Single Quantum Well Laser Diode

A new method using the broad spectrum of a 10 fs Ti:sapphire laser is demonstrated for measuring the gain spectra of semiconductor lasers with high and quantitative accuracy. Results are shown for an edge-emitting ridge-waveguide In0.05Ga0.95As single quantum well (SQW) laser. The device is studied from the absorption regime up to the strong gain regime recording both, TE and TM polarizations. The experiments are compared to the predictions of a microscopic model based on the semiconductor Bloch equations including microscopic scattering and dephasing terms. A very good quantitative agreement is obtained.

Threshold conditions for an ultraviolet wavelength GaN quantum-well laser

This paper describes an analysis of the threshold conditions for a GaN-AlGaN strained quantum-well (QW) laser. Gain spectra are computed using a many-body microscopic laser theory. The spontaneous emission rates are extracted from the gain spectra using a phenomenological expression based on energy conservation arguments. From the gain and spontaneous emission spectra, threshold current densities are estimated. Inhomogeneous broadening due to spatial variations in QW thickness are included in the analysis. Gain-current characteristics are determined for a number of laser heterostructure designs where the GaN QW width and Al composition of the AlGaN barrier material are varied.

Ballistic transport of electronic excitations and coherent light propagation in semiconductor quantum wells

SummaryThe transport of radiative and electronic excitations in coherently driven semiconductor quantum wells is analysed. On ultrashort time scales the spatial dynamics is determined by light propagation only, whereas for longer times the propagation of light and electronic excitations may be coupled. The theory is applied to the propagation of electronic excitations in the plane of a single quantum well and to polariton propagation in quantum well wave guides.