Roman Maciejko

Capture and escape in quantum wells as scattering events in Monte Carlo simulation

The capture and escape in quantum wells are considered as scattering events in Monte Carlo simulation. Explicit expressions are derived for these interaction rates which depend on carrier initial energy. The expressions are applied to calculate the electron overall capture time in a GRINSCH quantum well at 300 K.

Enhanced carrier injection efficiency from lateral current injection in multiple-quantum-well DFB lasers

A bidimensional simulation shows that the lateral carrier injection in etched active region of multiple-quantum-well DFB lasers represents a large fraction of the injected current, leading to improved carrier homogenization in the wells. This increases the average carrier density substantially and provides a much higher gain for the same injected current, depending on detailed device structure.

Linewidth broadening in a distributed feedback laser integrated with a semiconductor optical amplifier

The problem of the linewidth degradation in systems using distributed-feedback lasers together with strained-layer multi-quantum-well semiconductor optical amplifiers (SOAs) is examined. A modified expression for the linewidth in the case of anti reflection-coated SOA output facets is derived and simulation results are given in the case of output facets with a nonvanishing reflectivity. A numerical model combining finite-element calculations in the transverse x-y plane and a longitudinal model based on the Greens function method is used for that purpose.

Selective TE-TM mode pumping efficiencies for ridge-waveguide lasers in presence of stress

In ridge-waveguide InGaAsP lasers, TE-TM polarization switching with injection current can be caused by the presence of stress in the active layer coming from the deposition of stressed oxide and metallic films on the surface. It is shown that polarization switching takes its origin in the change of the mode pumping efficiency as the current varies. This conclusion has been reached with the help of a comprehensive semiconductor laser model that includes stress effects. Various stress regimes have been identified and it is also shown that the overall stress value in the active layer is the dominant effect, not so much the detailed stress profile. >

Relaxation oscillation frequency of DFB lasers with gain coupling

Using the spatially-dependent rate equations based on the Greens function analysis, we investigate the dependency of the relaxation oscillation frequency on the complex coupling coefficient and other parameters of gain-coupled DFB lasers by simultaneously considering spatial-hole-burning, gain saturation and gain compression. An explicit expression for the relaxation oscillation frequency for DFB lasers including the longitudinal spatial effects has been obtained. It is found that antiphase gain-coupling significantly enhances the local effective differential gain in the gain-coupled DFB laser and hence increases the relaxation oscillation frequency. We have also shown for the first time that the modal linewidth enhancement factor /spl alpha//sub M/ plays an important role in determining the relaxation oscillation frequency of gain-coupled DFB lasers, especially when the built-in index coupling is weak. >

Biaxial stress effects on the TE/TM polarization switching of InGaAsP ridge-waveguide lasers

TE/TM (transverse electric/magnetic) polarization switching in ridge-waveguide InGaAsP lasers is analyzed with due considerations to biaxial stress effects on both the waveguiding and gain properties of the device. The conditions of switching for several models are established. In particular, the gain expression for uniaxial stress is extended to include biaxial stress, and the differences between the different models are presented.<<ETX>>

Scattering rates due to lineal dislocations in heterostructures for the Monte Carlo charge transport simulation

We derived expressions for the scattering rates due to dislocations in pseudomorphic heterostructures. We gave explicit formulas for those scattering rates in the free and the confined states, depending on the initial carrier energy and on the component of the total wave vector parallel to the dislocations. We demonstrated that this new scattering process could affect the electron mean velocity by more than 30% from the ideal case treated commonly by the Monte Carlo simulators.

Analysis of an InGaAsP/InP twin-overlayed-waveguide switch

This paper examines the design considerations for a device combining vertical stacking of waveguides, carrier injection, and codirectional switching in InGaAsP/InP materials and demonstrates that many favorable features can be found in such a device, namely, an interaction length of about 408 /spl mu/m, switching with about 1 V with an injection current density of the order of 108-988 A/cm/sup 2/ and a channel isolation up to 25 db with an absorption loss of under 1 dB. We base our argument on a self-consistent numerical calculation. >

Optical front end for double-balanced homodyne receivers

An optical front end for double-balanced homodyne receiver is proposed. The device combines the function of a preamplifier, a 3-dB coupler, and a narrowband filter. A theoretical model is established and numerical results are presented. High gain and narrow bandwidth are predicted for this device. >

The performance of double active region InGaAsP lasers

The light-current characteristic and temperature behavior of the double-carrier-confinement (DCC) InGaAsP laser are shown to be largely determined by Auger recombination. The carrier distributions in the two active regions, especially their relative fractions, play a major role in device behavior. A self-consistent, comprehensive numerical laser model is used to analyze a set of devices showing that superlinearity and possibly bistability are due to saturable absorption in the second active region and that a high characteristic temperature is usually tied with a higher threshold current density because of substantial Auger recombination rates in this type of device. >