Frequency upconverted emissions centered at 526 and 547 nm from two thermodynamically coupled excited states of Er3+ doped in BaTiO3 nanocrystals were recorded in the temperature range from 322 to 466 K using a diode laser emitting at 980 nm as the excitation source. The ensemble measurements of the fluorescence intensity ratio (FIR) of the signals at 526 and 547 nm as a function of the temperature showed that the sensitivity (the rate in which the FIR changes with the temperature) of such sensor depends on the size of the nanocrystal. This is explained taking into consideration modifications of nonraditive relaxation mechanisms with the size of the nanocrystals.

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The effect of dopant concentration on the blue upconversion (UPC) emission of Tm(3+) -doped ZrO(2) nanocrystals under different excitation wavelengths in the red region is reported. The UPC emissions are due to the f-f electronic transitions from excited states (1)G(4) and (1)D(2) of Tm(3+). We observed a chromatic change in the UPC with tuning the excitation wavelength. The UPC emission bands at 475, 488, and 501 nm are observed under excitation at 649 nm, but bands centered at 454 and 460 nm are observed when the excitation wavelength is tuned to 655 nm. The UPC emission could be tuned from 501 to 454 nm ( approximately 47 nm) by changing the excitation wavelength from 649 to 655 nm ( approximately 6 nm). The pump power dependence of the emission bands at 475, 488, and 501 nm were investigated on excitation intensity at 649 nm, and the emission bands at 454 and 460 nm are investigated on excitation intensity at 655 nm, which confirms that all of these UPC emission lines are a two-photon absorption process.

Z -scan revealed thermal and electronic contributions for the nonlinear refractive index of highly stable colloid containing different concentrations of gold nanoparticles. Large enhancement factors were observed for values of n2 and dn∕dT of the colloid, due to the presence of the nanoparticles. Our results suggest that thermal effects will play an important role in the development of photonic applications involving nanostructured materials and in the investigation of nonlocal nonlinear phenomena.

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The third-order nonlinear optical properties of tellurite glasses with different compositions were investigated in the femtosecond regime at 810nm. Using the I-scan technique, positive nonlinear refractive indices of ∼10−15cm2∕W were measured. The authors also determined that nonlinear absorption was negligible for all studied samples. This result, added to their good chemical stability, indicates that tellurite glasses are promising materials for ultrafast photonic applications.

The nonlinear optical properties of two ionic liquids, 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMI]BF4) and 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMI]PF6), have been investigated using the Z-scan technique. These compounds are liquid at room temperature and present a strong ionic nature. Nonlinear refraction and absorption, and thermo-optical measurements for both ionic liquids were performed using two different laser wavelengths, 514 nm and 810 nm, in the continuous wave and femtosecond regimes, respectively. It was observed that those specimens have large negative nonlinear refractive indexes and thermo-optical coefficients, but nonlinear absorption was not observed. Different dispersion relations were observed depending on the ionic liquid anion, which may be related to the distinct structures of these compounds. This result indicates that ionic liquids are suitable media for the investigation of nonlocal nonlinear phenomena.

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