Nouvelle formulation de la fonction de transfert d'un laser à nanostructures quantiques pour les applications à la modulation haut-débit et aux phénomènes microscopiques non-linéaires

National audienceL'exploitation des semi-conducteurs de basse dimensionnalité permet d'améliorer les propriétés des composants optoélectroniques de par un meilleur confinement quantique des électrons et des trous. L'objectif de cette contribution est d'étudier théoriquement les propriétés dynamiques des lasers nano-structurés InAs/InP(311B). Une nouvelle expression de la fonction de transfert en intensité du laser est proposée pour les systèmes à îlots quantiques. Les modèles classiques pour les puits quantiques sont étudiés par comparaison ainsi que des données expérimentales sur des lasers à îlots

Modulation Response of Semiconductor Quantum-Dot Lasers

A new expression of the modulation transfer function is derived for quantum dot (QD) lasers. The analytical approach is based on a cascade relaxation model taking into account three QD energy levels such as the wetting layer (WL), the 1st excited state (ES) as well as the ground state (GS). From the analysis, we demonstrate that the carrier escape from (GS) to (ES) is responsible for a non-zero resonance frequency at low bias powers

Carrier escape from ground state and non-zero resonance frequency at low bias powers for semiconductor quantum-dot lasers

International audienceThe three-dimensional confinement of electrons and holes in the semiconductor quantum dot (QD) structure profoundly changes its density of states compared to the bulk semiconductor or the thin-film quantum well (QW) structure. The aim of this paper is to theoretically investigate the microwave properties of InAs/InP(311B) QD lasers. A new expression of the modulation transfer function is derived for the analysis of QD laser modulation properties based on a set of four rate equations. Analytical calculations point out that carrier escape from ground state (GS) to excited state (ES) induces a non-zero resonance frequency at low bias powers. Calculations also show that the carrier escape leads to a larger damping factor offset as compared to conventional QW lasers. These results are of prime importance for a better understanding of the carrier dynamics in QD lasers as well as for further optimization of low cost sources for optical telecommunications

Impacts of Wetting Layer and Excited State on the Modulation Response of Quantum-Dot Lasers

International audienceThe modulation response of quantum-dot (QD) lasers is studied. Based on a set of four rate equations, a new analytical modulation transfer function is developed via a small-signal analysis. The transfer function can clearly describe the impacts of the wetting layer and the excited states: finite carrier capture and carrier relaxation times as well as the Pauli blocking limits the modulation bandwidth. The definitions of the resonance frequency and the damping factor of QD lasers are also improved. From the analysis, it is demonstrated that carrier escape from the ground state to the excited states leads to a nonzero resonance frequency at low bias powers associated to a strong damping factor

Influence of the Linewidth Enhancement Factor on the Modulation Response of a Nanostructure based Semiconductor Laser Operating under External Optical Feedback

International audienceThe knowledge of the linewidth enhancement factor (alpha(H)-factor) is very important to understand the performance of semiconductor lasers. It affects several fundamental aspects such as the linewidth, the laser's behavior under optical feedback, the chirp under direct modulation and the occurrence of the filamentation. The dramatic variation in the alpha(H)-factor that has been reported for quantum dot lasers makes them an interesting subject for optical feedback studies. In the particular case of QD lasers, the carrier density is not clearly clamped at threshold. The lasing wavelength can switch from the ground state to the excited state as the current injection increases meaning that a carrier accumulation occurs in the ES even though lasing in the GS is still occurring. The purpose of the paper is to show that the exploitation of the nonlinear properties arising from quantum nanostructure based semiconductor lasers operating under external optical feedback can lead, under specific conditions, to a bifurcation of the modulation properties. Starting from the generalized rate equations under optical feedback, the laser's modulation response is determined. Under the short external cavity assumption, calculations show that large variations of the alpha(H)-factor can contribute to improve the dynamical properties such as the relaxation frequency as well as the laser's bandwidth. On the contrary, assuming the long external cavity situation, numerical results show that even small reflections in the percent range when combined to significant variations of the alpha(H)-factor alter the laser's modulation response

From basic physical properties of InAs/InP quantum dots to state of the art semi-empirical modelling of 1.55mm directly modulated QD Lasers: an overview

From basic physical properties of InAs/InP quantum dots to state of the art semi-empirical modelling of 1.55mm directly modulated QD Lasers: an overvie

Intensity modulation response of injection-locked quantum cascade lasers

International audienceThe intensity modulation (IM) property of an optical injection-locked quantum cascade (QC) laser is theoretically investigated via a three-level rate equation model. The locking regime is obtained based on the local bifurcation theory. It is shown that the injection-locked QC laser exhibits a rather flat modulation response at zero detuning, whose bandwidth increases with the injection level. In contrast to interband lasers, both positive and negative detunings enhance the modulation bandwidth. Besides, a large linewidth enhancement factor (LEF) can increase the peak amplitude in the response. Moreover, it is found that no frequency dip occurs in the IM response of injection-locked Q

Controlling the pre-resonance frequency dip in the modulation response of injection-locked quantum dot lasers

International audienceControlling the pre-resonance frequency dip in the modulation response of injection-locked quantum dot laser

Modelling the gain compression effects in semiconductor quantum-dot lasers through a new modulation transfer function

International audienceModelling the gain compression effects in semiconductor quantum-dot lasers through a new modulation transfer functio