A spectroscopic method, which enables characterization of a single isolated quantum dot and a quantum wave function interferometry, is applied to an exciton discrete excited state in an InGaAs quantum dot. Long coherence of zero-dimensional excitonic states made possible the observation of coherent population flopping in a 0D excitonic two-level system in a time-domain interferometric measurement. Corresponding energy splitting is also manifested in an energy-domain measurement.

InGaN multiple quantum wells were grown on InGaN underlying layers 50 nm thick by metalorganic vapor phase epitaxy. Photoluminescence (PL) measurements were performed by selective excitation of the quantum wells under a weak excitation condition. The PL intensity was almost constant at temperatures ranging from 17 to 150 K. Assuming that the internal quantum efficiency (ηint) equals unity at 17 K, we obtained ηint as high as 0.71 even at room temperature. The reason for the high ηint is the reduction of nonradiative recombination centers by the incorporation of indium atoms into the underlying layer.

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We demonstrate optically pumped telecom-band lasing in single InAs/InP nanowires at room temperature.

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