Abstract
We demonstrate a new method to realize the population inversion of a single InGaAs/GaAs quantum dot excited by a laser pulse tuned within the neutral exciton phonon sideband. In contrast to the conventional method of inverting a two-level system by performing coherent Rabi oscillation, the inversion is achieved by rapid thermalization of the optically dressed states via incoherent phonon-assisted relaxation. A maximum exciton population of 0.67±0.06 is measured for a laser tuned 0.83meV to higher energy. Furthermore, the phonon sideband is mapped using a two-color pump-probe technique, with its spectral form and magnitude in very good agreement with the result of path-integral calculations.
Highlights
It is a basic tenet of laser physics that a population inversion cannot be achieved through incoherent excitation of a two-level atom
We demonstrate a new method to realize the population inversion of a single InGaAs=GaAs quantum dot excited by a laser pulse tuned within the neutral exciton phonon sideband
If the two-level atom is coupled to a vibrational continuum, it has been predicted that inversion can be possible even in the incoherent regime through the interaction of the dressed states with the Boson bath [2]
Summary
It is a basic tenet of laser physics that a population inversion cannot be achieved through incoherent excitation of a two-level atom. Phonon-Assisted Population Inversion of a Single InGaAs=GaAs Quantum Dot by Pulsed Laser Excitation
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