S. Ohkouchi

Investigation of the Spectral Triplet in Strongly Coupled Quantum Dot–Nanocavity System

We experimentally investigated the excitation power dependence of a strongly coupled quantum dot (QD)–photonic crystal nanocavity system by photoluminescence measurements. At a low excitation power regime, we observed a vacuum Rabi doublet emission at the QD–cavity resonance condition. With increasing excitation power, in addition to the doublet, a third emission peak appeared. This observed spectral change is unexpected from conventional atomic cavity quantum electrodynamics. The observations can be attributed to featured pumping processes in the semiconductor QD–cavity system.

Enhancement of Valence Band Mixing in Individual InAs/GaAs Quantum Dots by Rapid Thermal Annealing

We measure polarization resolved photoluminescence from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) over a wide range of energies in two samples: one as-grown, the other subjected to rapid thermal annealing (RTA). Using the linear polarization of the X+ emission as a probe of the valence band mixing (VBM), we find that RTA enhances QD VBM, attributed to the increase in QD height. We complement our measurements with 8-band kp calculations, which suggest the increase in height on annealing is responsible for this enhancement.

Neutralization of positively charged excitonic state in single InAs quantum dot by Si delta doping

Positively charged excitonic state in single InAs quantum dot (QD) has been neutralized by Si delta doping and the optical properties of the fabricated samples are characterized by micro-photoluminescence measurements (μ-PL) at low temperature. An InAs QD sample having dominant emissions from positively charged excitonic states is prepared for a reference. By optimizing Si delta doping conditions, positively charged QDs are neutralized successfully and distinctive emissions from neutral exciton and biexciton from single QDs are achieved. For excessive doping condition, μ-PL spectra show optical degradation of lowering of peak intensity and broadening of peak width as doping concentration increases.