Articles you may be interested inObservations of near-zero linewidth enhancement factor in a quantum-well coupled quantum-dot laser High-gain coupled InGaAs quantum well InAs quantum dot AlGaAs-GaAs-InGaAs-InAs heterostructure diode laser operation

The correlations between photons generated by nonlinear optical processes offer advantages for many quantum technology applications, including spectroscopy, imaging, and metrology. Here, we use spontaneous four-wave mixing in a birefringent single-mode fiber pumped by a tunable pulsed laser as a broadly tunable source of phase-matched non-degenerate photon pairs for spectroscopy. The pairs are tunable such that the idler beam measures the transmittance spectrum of a sample in the near infrared, while the visible signal beam independently reports correlation information. By the time-resolved counting of both signal and idler photons, we use photon-number correlations to remove uncorrelated noise from the probe beam. Here, we have used heralded spectroscopy to measure the absorption spectrum of gallium arsenide near its band edge, despite the idler photon spectrum being dominated by a large background from spontaneous Raman scattering.

Threading dislocations in thick layers of InxGa1-xN (5% < x < 15%) have been investigated by means of cathodoluminescence, time-resolved cathodoluminescence and molecular dynamics. We show that indium atoms segregate near dislocations in all the samples. This promotes the formation of InN In chains and atomic condensates which localize carriers and hinder non-radiative recombination at dislocations. We note however that the dark halo surrounding the dislocations in the cathodoluminescence image becomes increasingly pronounced as the indium fraction of the sample increases. Using transmission electron microscopy, we attribute the dark halo to a region of lower indium content formed below the facet of the V-shaped pit that terminates the dislocation in low composition samples (x < 12%). For x > 12%, the facets of the V-defect featured dislocation bundles instead of the low indium fraction region. In this sample the origin of the dark halo may relate to a compound effect of the dislocation bundles, of a variation of surface potential and perhaps of an increase in carrier diffusion length.

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