Thermal conductivity determination of erbium-doped crystals measured by spatially resolved confocal luminescence.

Thermal conductivity of Er3+-doped yttrium aluminum perovskite has been obtained by the use of laser induced temperature distribution and time-independent heat propagation equations. By using the spatially resolved microluminescence technique, the fluorescence spectra on the sample surface were mapped during the laser focused heating process, and the local temperature was measured at different spots on the sample surface with micrometric resolution. Significant information about the temperature profile was obtained following the maximum temperature of the laser spot and the behavior of the heat diffusion on the surface of the irradiation side. These data were finally used to feed the heat propagation equations from where the thermal conductivity was evaluated.

Preparation and quantitative characterization of polydimethylsiloxane optical phantoms with zinc-phthalocyanine dye absorbers.

We described a method for the preparation of polydimethylsiloxane (PDMS) phantoms to mimic the optical properties of biologic tissues at distinct wavelengths ranging from the visible to the near-infrared spectra. The present method for fabricating solid optical tissue phantoms using zinc-phthalocyanine chromophores has demonstrated high photostability with optical absorption coefficients up to 1.0 mm-1, making this phantom proper with absorption bands ranging from 600 to 850 nm. It also happens that the chromophore absorption coefficient is linear as a function of its concentration inside the previous optical window. The optical scattering properties were quantitatively selected by adding TiO2 particle concentrations to the PDMS phantom. Thus, the quantitative optical properties of absorption and scattering for a large-batch fabrication were demonstrated, making the zinc-phthalocyanine phantoms suitable for use as a reference standard.

Carrier transport investigation in short-wavelength InAs/AlGaAs quantum dots.

Spatially resolved photoluminescence has been used to investigate the details of the carrier capture and recombination dynamics in InAs/AlGaAs self-assembled quantum dots. The spatial PL distribution displays a Gaussian-like profile, whose width depends upon the temperature and detection energy being analyzed. The results give evidence of carrier thermalization between dots with different sizes. The effects of carrier transport in the quantum dot (QD) structure and carrier capture cannot be separated. The results can be modeled by assuming a carrier hopping process.