Olga A. Dyatlova

Time-resolved amplified spontaneous emission in quantum dots

In time-resolved experiments at InGaAs/GaAs quantum-dots-in-a-well (DWELL) semiconductor optical amplifiers, pump-probe of the ground state (GS) population, and complementary measurement of the amplified spontaneous emission of the excited state (ES) population, we are able to separate the early subpicosecond dephasing dynamics from the later picosecond population relaxation dynamics. We observe a 10 ps delay between the nonlinear GS pulse amplification and the subsequent ES population drop-off that supports the dominance of a direct two dimensional reservoir-GS capture relaxation path in electrically pumped quantum-dot-DWELL structures.

Ultrafast Relaxation Dynamics via Acoustic Phonons in Carbon Nanotubes

Carbon nanotubes as one-dimensional nanostructures are ideal model systems to study relaxation channels of excited charged carriers. The understanding of the ultrafast scattering processes is the key for exploiting the huge application potential that nanotubes offer, e.g., for light-emitting and detecting nanoscale electronic devices. In a joint study of two-color pump-probe experiments and microscopic calculations based on the density matrix formalism, we extract, both experimentally and theoretically, a picosecond carrier relaxation dynamics, and ascribe it to the intraband scattering of excited carriers with acoustic phonons. The calculated picosecond relaxation times show a decrease for smaller tube diameters. The best agreement between experiment and theory is obtained for the (8,7) nanotubes with the largest investigated diameter and chiral angle for which the applied zone-folded tight-binding wave functions are a good approximation.

Specific features of the CuI nanocrystal structure in photochromic glasses

The absorption spectra of CuI nanocrystals with an average radii of 5.3 and 6.2 nm in photochromic glass matrix have been studied in the temperature range 38–300 K. It has been established that the copper iodide nanocrystals, like copper chloride and copper bromide nanocrystals of the same sizes, predominantly crystallize in a nonequilibrium form different from the stable low-temperature cubic modification. The structure of metastable modifications of copper halide nanocrystals in photochromic glasses has been discussed.

Structure of copper halide nanocrystals in photochromic glasses

The crystal structure of CuCl nanocrystals with effective radii ranging from 2.4 to 18.5 nm in photochromic glasses heat treated under different conditions is investigated using exciton spectroscopy, x-ray powder diffraction, and small-angle x-ray scattering. It is revealed that the size dependence of the energy of the Z3 exciton exhibits an anomalous behavior. The results obtained suggest that small-sized CuCl nanocrystals can crystallize in a modification different from the stable cubic modification.

Compact electrically tunable delay generator on silicon

Feasibility of a tunable delay of optical data streams is proved by experimentally validating a hybrid fiber/integrated realization. Ultimate design can provide delays of more than 200 ps in an area of about 0.4 mm2.

Scattering of electrons with acoustic phonons in single-walled carbon nanotubes

We perform two color pump-probe experiments on nanotubes (8,7);(10,2);(11,3);(12,1). The dynamics were analyzed for three decay constants. A density-matrix formalism reveals that the fastest component is caused by intraband carrier-phonon scattering.

The excitonic capture path in electrically pumped quantum dots using time-resolved amplified spontaneous emission

We combined two different time resolved measurements to determine the excitonic capture path in electrically pumped InGaAs/GaAs quantum dots (QDs) in-a-well (DWELL). The QDs form the active medium of a Semiconductor Optical Amplifier (SOA), a waveguide based electrically pumped device designed to amplify light around 1.3 µm.