Dynamic phase response and amplitude-phase coupling of self-assembled semiconductor quantum dots

Abstract

The optical excitation of semiconductor gain media introduces both gain and refractive index changes, commonly referred to as amplitude-phase coupling. Quantum-confined structures with an energetically well separated carrier reservoir usually exhibit a decreased amplitude-phase coupling compared to bulk materials. However, its magnitude and definition is still controversially discussed. We investigate the fundamental processes influencing the amplitude-phase coupling in semiconductor quantum-dot media using a coupled-carrier rate-equation model. We are able to analyze the dependence on the electronic structure and suggest routes towards an optimization of the dynamic phase response of the gain material.

Ultra-Short Pulse Generation in a Three Section Tapered Passively Mode-Locked Quantum-Dot Semiconductor Laser

“…Upon being reflected at the back facet of the laser as seen in the middle of Fig. 4(a), the pulse travels back through the straight gain section, where the ultra fast carrier relaxation from the QD excited state to the ground state 39,40 , has restored the gain everywhere except right next to the facet. There, waveguide losses still dominate, as indicated by the small vertical blue region in the middle of Fig.…”

“…We therefore follow the ideas of 35,49,57,58 and propose a model that couples a traveling-wave equation for the propagation of the electric field via effective Maxwell-Bloch equations to microscopically motivated rate equations that describe the electronic degrees of freedom in the active medium. To achieve the required computational efficiency, we describe the quantum dots by averaging over the inhomogeneously broadened quantum dots 35,40,59 and neglect the effects of spatial hole burning 57,58 . In the following, we present the derivation of our model.…”

“…Figure 7(b) shows a sketch of the different levels and their interaction via scattering processes. Their dynamics at each spatial coordinate are described by a set of coupled rate equations 40 with the pump current density J , the characteristic carrier lifetimes τ GS,ES,n , the factor 4 for spin and ES degeneracy, the net carrier capture from the wetting layer and the net intra-dot carrier relaxation R rel 38,63,64 . The net intra-dot relaxationincludes Pauli-blocking terms and a Boltzmann-factor with the energy difference Δ ε ESGS between the QD excited and ground state and the effective temperature T to to account for detailed balance between the in and out-scattering processes.…”

Spatio-Temporal Modeling and Device Optimization of Passively Mode-Locked Semiconductor Lasers

“…The quantum-dot excited state is assumed to be two-fold degenerate with respect to the quantum-dot ground state. The dynamics at each spatial coordinate are described by a set of coupled rate equations [LIN17a]…”

Mode-locking Instabilities for High-Gain Semiconductor Disk Lasers Based on Active Submonolayer Quantum Dots

“…The heavier holes are better confined in the In-rich islands, while the electron wavefunction sees only the lateral (In x Ga 1-x )As QW barriers and is delocalized over several InAs agglomerations. This limited confinement in combination with the high areal densities of localization centers enhances a strong interdot coupling in contrast to SK QDs [43]. Furthermore, the efficient lateral coupling with an optically inactive but fast accessible carrier reservoir can provide a very fast gain recovery, but can also induce significant refractive index changes after an optical excitation [44].…”