Complementary detection of confined acoustic phonons in quantum dots by coherent phonon measurement and Raman scattering

Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass by femtosecond pump-and-probe. The size dependence of the oscillation is investigated. Distinct low-frequency peaks are observed in Raman spectrum for the same samples. The size-dependence of the frequencies is well explained by elastic sphere model, but the observed modes are different to each other for coherent phonon and Raman scattering. Coherent phonon measurement and Raman scattering are found to give complementary information on confined acoustic phonons in this system

Strong confinement of PbSe and PbS quantum dots

We synthesized PbSe and PbS quantum dots in strong-confinement regime, and measured energy relaxation time by using pump-and-probe experiments. Energy relaxation time of PbSe dots in phosphate glasses showed clear correlation with the average radius. Smaller dots were shown to have shorter decay times. This dependence is ascribed to the relaxation to the surface of the dots

Poling of Glasses Using Resistive Barrier Discharge Plasma

A technique for poling of glasses using a resistive barrier discharge plasma in the atmosphere in a gap of hundreds of microns is presented. Measurements of the polarization current, second harmonic generation, and IR spectra of poled soda-lime glass slides show that voltage sufficient to ignite plasma discharge provides efficient poling, whereas for lower voltages the poling effect is close to zero. We attributed this to the large number of hydrogen/hydronium ions generated from atmospheric water vapor by the plasma discharge in the gap, which penetrate into the glass. We also developed a simple model of poling according to Ohm’s law, analyzed the temporal dependencies of the polarization current and, basing on the model, estimated mobilities of hydrogen/hydronium and sodium ions in the glass: μH = (2.4 ± 0.8) × 10−18 m2V−1s−1 and μNa = (4.8 ± 1.8) × 10−15 m2V−1s−1. The values obtained are very close to the known literature data

Nanoscale self-arranged layers of silver nanoparticles in glass

We characterized changes in the composition of subsurface layer of silver ion-exchanged soda-lime glass during annealing in hydrogen atmosphere. The formation of tens of nanometers distanced layers of silver nanoparticles in the glass at temperature of 300 °C has been revealed. Performed numerical modeling of the process demonstrates a good qualitative agreement with the experiment. This is of interest for simple formation of 3D-optoplasmonic structures, Bragg gratings or photonic crystals