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

Diffusive Formation of Au/Ag Alloy Nanoparticles of Governed Composition in Glass

For the first time we show that the introduction of silver ions in the glass containing gold nanoparticles (NPs) and additional heat treatment of the glass in the air lead to the formation of Au/Ag alloy NPs. The proposed approach makes it possible to position localized surface plasmon resonance of the NPs by selecting the heat treatment temperature, which determines the silver proportion in the alloy NPs. This allows for expanding customizability of NPs for applications in surface-enhanced Raman scattering spectroscopy, catalysis and biochemistry. Developed technique benefits from the presence of silver in the glass in ionic form, which prevents the oxidation of silver and provides stable preparation of Au/Ag alloy NPs

The remarkable transformation of nanoripples in glass-metal nanocomposite

We report the linear-to-circular transformation of high spatial frequency (HSF) ripples formed on the surface of a glass with embedded silver nanoparticles under irradiation with 120 fs long pulses at the wavelength of 800 nm. In the experiments, at the ablation threshold of 1.28 J/cm2, the HSF ripples with the period of ∼300 nm were oriented along the polarization of the laser beam. However, we found that the nanoripples pattern is gradually transforming from linear to an untypical circular one when the pulse energy increases. The ripples take nearly perfect circular shape at the pulse energy of ∼8.0 μJ, which corresponds to the fluence of 1.5 J/cm2

Non-resonant enhancement of second-harmonic generation from metal nanoislands coated with dielectric layers

Second-harmonic generation from gold nanoisland films increases with the dielectric TiO2 coating thickness. This occurs although the plasmon resonance shifts away from the second-harmonic wavelength, due to enhanced non-resonant local fields at the fundamental wavelength.acceptedVersio