Investigation of photoluminescence kinetics CuInS2/ZnS quantum dots

The kinetics of photoluminescence of CuInS2/ZnS quantum dots at room temperature has been studied. We show that the parameters of the photoluminescence band of our quantum dots, i.e. its position and FWHM, do not depend on the delay time after the excitation laser pulse. These may suggest the spectral diffusion of photoluminescence of CuInS2/ZnS quantum dots due to hole localization at different Cu sites.

Fluorescence and Time-Delayed Lasing during Single Laser Pulse Excitation of a Pendant mm-Sized Dye Droplet

Fluorescence and lasing emission that are produced separately in time during excitation laser pulse for an mm-sized Rhodamine 6G dye-water droplet are reported. The droplet acts as a quasi-spherical closed optical resonator and due to multiple internal reflections, the resonant amplified emission is delayed with respect to fluorescence emission. Measurements of the temporal evolution of the droplet’s emission were performed by varying the signal acquisition gate width and gate delay with respect to the pumping pulse. The droplet emission spectra are structured in two bands which appear one after the other in time: first, the fluorescence emission band which follows pumping laser pulse time shape and then a second band, the lasing band, placed at shorter wavelengths and formed in time after the peak of the pumping laser pulse intensity, on the pulse tail. The lasing threshold pumping intensity is much lower than those for typical dye lasers.

The Velocity and Temperature Measurement of a Water Flow in the Wire-Wrapped 7-Rods Bundle System in FBR

Phosphorescence has been applied to measure the temperature. The intensity and the lifetime of phosphor depend on the temperature due to the quenching effect of the phosphor. In the present study, the temperature sensitive particles (TSParticles) with metal complex, phosphor molecules, were synthesized. TSParticles can be also particles for the particle image velocimetry. The particles were illuminated by a pulse laser at 20Hz. A high speed camera was applied to record 30 particle images at intervals of 25∼50 micro seconds (20∼40kHz) for each excitation laser pulse. From each series of images the velocity/temperature field was calculated. The TSParticle technique was applied to measure the velocity/temperature distribution of a water flow in a wire-wrapped rod bundle system, which briefly simulated the fuel rods system in FBR. The working fluid was water and the aim of this study was to contribute to an estimation and a certification of results of numerical simulation for the safety design of the FBR.

ULTRAFAST DYNAMICS OF COULOMB CORRELATION EFFECTS IN NON-EQUILIBRIUM FERMI SEAS

By spectrally resolving the transient four-wave mixing (FWM) signal and the differential transmission signal arising from electron-hole pairs optically excited into the continuum of a GaAs/AlGaAs quantum well structure, we directly measure the dynamics of the quantum coherence among such interacting carriers. We observe a dynamic blue-shift of the coherent FWM emission spectrum with respect to the excitation laser pulse. We interpret our results in terms of dynamic Coulomb correlation effects arising in non-equilibrium degenerate electron-hole systems.