We report on the synthesis of single-crystalline tellurium nanowires with different aspect-ratios prepared via facile surfactant-assisted synthesis under mild conditions. Short and long Te nanowires were synthesized by the reduction of tellurium dioxide by hypophosphorous acid with the assistance of polyoxyethylene (23) laurylether and cetyltrimethylammonium bromide, respectively. We obtained uniform single-crystal Te nanowires with diameter below 30 nm and tunable length from 600 nm to 5 µm. Short and long Te nanowires showed remarkable nonlinear absorption and their third-order nonlinear optical properties were investigated by the Z-scan technique with single 80 ps laser pulses at 532 nm. For the first time, it was observed a distinguished switching behavior from saturated absorption to reverse saturated absorption as a function of the laser intensity in one-dimensional Te nanostructures. Although both short and long Te nanowires display such interesting behavior, the short ones exhibited superior optical limiting performance.

Samples of (1 – x)SiO2:xGeO2 compositions, containing x = 10 and 20, and doped with Er3+, were prepared by a simple sol-gel route. Homogeneous and transparent gels were synthesized and xerogels were obtained by gel annealing from 700 ºC to 1100 ºC. Films exhibiting high transmittance in the visible and near infrared were deposited by spin-coating technique using the colloidal precursors. The materials were characterized structurally and microstructurally by some techniques. Spherical completely amorphous and tetragonal GeO2 nanocrystals from 3.7 nm to 25.0 nm in diameter embedded in silica-rich amorphous phase materials were obtained. The optical properties were studied by transmission spectra from ultraviolet to near infrared region, photoluminescence measurements in the infrared region, and the average lifetime of the metastable state 4I13/2 of Er3+ ions were determined. The 1 mol% Er3+ doped host with x = 20 have an infrared emission 4.9 times higher than the compound containing x = 10, and the Er3+4I13/2 level present lifetime between 15.0 ms and 7.5 ms. The optical band gap and refractive index values were determined, as well as the Sellmeier parameters. Finally, rib channel waveguides using femtosecond laser etching technique on silica substrates were obtained with width of 15 mm. The 1 mol% Er3+ doped 80SiO2:20GeO2 compounds can be applicable in integrated optical systems.