RESUMEN
We report a systematic investigation on the temperature dependence of fluorescence decay dynamics of infrared emitting colloidal Ag2S nanocrystals (NCs) with different surface coatings. The drastic lifetime reduction in the biological temperature range (20-50 °C) makes Ag2S NCs outstanding candidates for high sensitivity subcutaneous lifetime-based thermal sensing in the second biological window (1000-1400 nm). Indeed, the lifetime thermal sensitivity of Ag2S NCs has been found to be as large as 3-4% °C-1 at an operating wavelength of 1250 nm. Their application for lifetime-based luminescence nanothermometry has been demonstrated through simple ex vivo experiments specially designed to elucidate the magnitude of subcutaneous thermal gradients. Experimental data were found to be in excellent agreement with numerical simulations.
RESUMEN
We report the formation of optical waveguides in the self-Raman Nd:YVO(4) laser crystal by femtosecond laser inscription. The confocal fluorescence and Raman images have revealed that the waveguide is constituted by a locally compressed area in which the original fluorescence and Raman gains of the Nd:YVO(4) system are preserved. Thus the obtained structures emerge as promising candidates for highly efficient self-Raman integrated laser sources.
RESUMEN
The LiNbO(3) congruent crystals doped with small Nd concentrations, <1 mol% Nd, and co-doped with Mg ions, 0-9 mol% Mg, were systematically investigated by means of micro-Raman spectroscopy in the Y and Z crystal directions. Results obtained from an undoped congruent crystal, an Nd-doped crystal, a Mg-doped crystal and Nd, Mg-co-doped crystals are compared. From the analyses of the results obtained in the Y direction, the Nd and Mg content dependence of the two lowest-Raman A(1)(TO(1)) and A(1)(TO(2)) modes, the half-width composition and the area ratio of the A(1)(TO(4)) and E(TO(8)) bands, we reached several conclusions about the incorporation mechanism of the Nd and Mg ions into the LiNbO(3) lattice. Likewise the Raman shift and half-width of the E(TO(1)) and E(TO(7)) modes were investigated in the Z direction. Results indicate that Mg and Nd ions are located in the Li site for low doping concentrations and for larger concentrations there is a replacement in both Li and Nb ion sites.
RESUMEN
The temperature and compositional dependences of thermo-optical properties of neodymium doped yttrium aluminum garnet (YAG) crystals and fine grain ceramics have been systematically investigated by means of time-resolved thermal lens spectrometry. We have found that Nd:YAG ceramics show a reduced thermal diffusivity compared to Nd:YAG single crystals in the complete temperature range investigated (80-300 K). The analysis of the time-resolved luminescent properties of Nd(3+) has revealed that the reduction in the phonon mean free path taking place in Nd:YAG ceramics cannot be associated with an increment in the density of lattice defects, indicating that phonon scattering at grain boundaries is the origin of the observed reduction in the thermal diffusivity of Nd:YAG ceramics. Finally, our results showed the ability of the time-resolved thermal lens to determine and optimize the thermo-optical properties of Nd:YAG ceramic based lasers.
RESUMEN
We report on a simple and accurate method for determination of thermo-optical and spectroscopic parameters (thermal diffusivity, temperature coefficient of the optical path length change, pump and fluorescence quantum efficiencies, thermal loading, thermal lens focal length, etc) of relevance in the thermal lensing of end-pumped neodymium lasers operating at 1.06- and 1.3- microm channels. The comparison between thermal lensing observed in presence and absence of laser oscillation has been used to elucidate and evaluate the contribution of quantum efficiency and excited sate absorption processes to the thermal loading of Nd:YAG lasers.