Impact of the carrier relaxation paths on two-state operation in quantum dot lasers

Abstract

We study InGaAs QD laser operating simultaneously at ground (GS) and excited (ES) states under 30ns pulsed-pumping and distinguish three regimes of operation depending on the pump current and the carrier relaxation pathways. An increased current leads to an increase in ES intensity and to a decrease in GS intensity (or saturation) for low pump range, as typical for the cascade-like pathway. Both the GS and ES intensities are steadily increased for high current ranges, which prove the dominance of the direct capture pathway. The relaxation oscillations are not pronounced for these ranges. For the mediate currents, the interplay between the both pathways leads to the damped large amplitude relaxation oscillations with significant deviation of the relaxation oscillation frequency from the initial value during the pulse.

Influence of potential well thickness on the carrier transport characteristics of InGaAs quantum dot laser diodes

“…14 In order to realize the controllable transition of the ground state and excited state under electrical excitation, the electron relaxation process needs to be further studied. 15,16 Therefore, the composite structural active zone of QDs and quantum wells is an effective candidate to capture more carriers for injecting into QDs. 17 Moreover, the quantum well in the QD/quantum well composite structural active zone can not only improve the carrier injection efficiency but also reduce the interfacial strain, which could decrease carrier and optical losses.…”