14 research outputs found
Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation
The impact of ground state amplification on the laser emission of In(Ga)As
quantum dot excited state lasers is studied in time-resolved experiments. We
find that a depopulation of the quantum dot ground state is followed by a drop
in excited state lasing intensity. The magnitude of the drop is strongly
dependent on the wavelength of the depletion pulse and the applied injection
current. Numerical simulations based on laser rate equations reproduce the
experimental results and explain the wavelength dependence by the different
dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously
broadened quantum dots. At high injection levels, the observed response even
upon perturbation of the lasing sub-ensemble is small and followed by a fast
recovery, thus supporting the capacity of fast modulation in dual-state
devices
Broadband semiconductor light sources operating at 1060 nm based on InAs:Sb/GaAs submonolayer quantum dots
In this paper, we investigate the potential of submonolayer-grown InAs:Sb/GaAs quantum dots as active medium for opto-electronic devices emitting in the 1060 nm spectral range. Grown as multiple sheets of InAs in a GaAs matrix, submonolayer quantum dots yield light-emitting devices with large material gain and fast recovery dynamics. Alloying these structures with antimony enhances the carrier localization and red shifts the emission, whereas dramatically broadening the optical bandwidth. In a combined experimental and numerical study, we trace this effect to an Sb-induced bimodal distribution of localized and delocalized exciton states. While the former do not participate in the lasing process, they give rise to a bandwidth broadening at superluminescence operation and optical amplification. Above threshold laser properties like gain and slope efficiency are mainly determined by the delocalized fraction of carriers
Biexciton-mediated modulation response of colloidal quantum dots deposited on a silicon nitride waveguide at high laser excitation rate
We develop a sensitive collinear pump-probe technique to resolve small amplitude and phase modulations of laser pulses in hybrid PbS/CdS-quantum-dot-SiN waveguides. It shows that at high excitation rate biexciton creation governs the optical interaction