Thiago A. A. de Assumpção

Enhanced luminescence of Tb3+/Eu3+ doped tellurium oxide glass containing silver nanostructures

We report on energy transfer studies in terbium (Tb3+)—europium (Eu3+) doped TeO2–ZnO–Na2O–PbO glass containing silver nanostructures. The samples excitation was made using ultraviolet radiation at 355 nm. Luminescence spectra were recorded from ≈480 to ≈700 nm. Enhanced Eu3+ luminescence at ≈590 nm (transition D50−F71) and ≈614 nm (transition D50−F72) are observed. The large luminescence enhancement was obtained due to the simultaneous contribution of the Tb3+–Eu3+ energy transfer and the contribution of the intensified local field on the Eu3+ ions located near silver nanostructures.

Femtosecond third-order nonlinear spectra of lead-germanium oxide glasses containing silver nanoparticles.

This work reports on the spectral dependence of both nonlinear refraction and absorption in lead-germanium oxide glasses (PbO-GeO₂) containing silver nanoparticles. We have found that this material is suitable for all-optical switching at telecom wavelengths but at the visible range it behaves either as a saturable absorber or as an optical limiter.

Infrared-to-visible upconversion emission in Er3+ doped TeO2-WO3-Bi2O3 glasses with silver nanoparticles

The influence of silver nanoparticles (NPs) on the frequency upconversion luminescence in Er3+ doped TeO2-WO3-Bi2O3 glasses is reported. The effect of the NPs on the Er3+ luminescence was controlled by appropriate heat-treatment of the samples. Enhancement up to 700% was obtained for the upconverted emissions at 527, 550, and 660 nm, when a laser at 980 nm is used for excitation. Since the laser frequency is far from the NPs surface plasmon resonance frequency, the luminescence enhancement is attributed to the local field increase in the proximity of the NPs and not to energy transfer from the NPs to the emitters as is usually reported. This is the first time that the effect is investigated for tellurite-tungstate-bismutate glasses and the enhancement observed is the largest reported for a tellurium oxide based glass.

Enhanced Optical Properties of Germanate and Tellurite Glasses Containing Metal or Semiconductor Nanoparticles

Germanium- and tellurium-based glasses have been largely studied due to their recognized potential for photonics. In this paper, we review our recent studies that include the investigation of the Stokes and anti-Stokes photoluminescence (PL) in different glass systems containing metallic and semiconductor nanoparticles (NPs). In the case of the samples with metallic NPs, the enhanced PL was attributed to the increased local field on the rare-earth ions located in the proximity of the NPs and/or the energy transfer from the metallic NPs to the rare-earth ions. For the glasses containing silicon NPs, the PL enhancement was mainly due to the energy transfer from the NPs to the Er3+ ions. The nonlinear (NL) optical properties of PbO-GeO2 films containing gold NPs were also investigated. The experiments in the pico- and subpicosecond regimes revealed enhanced values of the NL refractive indices and large NL absorption coefficients in comparison with the films without gold NPs. The reported experiments demonstrate that germanate and tellurite glasses, having appropriate rare-earth ions doping and NPs concentration, are strong candidates for PL-based devices, all-optical switches, and optical limiting.

White light generation in Tm3+/Ho3+/Yb3+ doped PbO-GeO2 glasses excited at 980 nm

We report white light generation (WLG) in Tm3+/Ho3+/Yb3+ doped PbO-GeO2 glass under continuous-wave excitation at 980 nm. Intense blue (≈477 nm), green (≈545 nm), and red (≈ 658 nm) emissions were simultaneously observed at room temperature. The blue light is mainly due to the Tm3+ transition 1G4 → 3H6. The green emission is due to the Ho3+ transitions (5S2, 5F4) → 5I8 and the red luminescence is due to the Ho3+ transition 5F5 → 5I8 and transition 1G4 → 3F4 associated to the Tm3+ ions. Energy transfer processes from Yb3+ to Ho3+ and Yb3+ to Tm3+ ions were responsible for the WLG. Adjusting the relative concentration of the rare-earth (RE) ions, we could obtain emission in the white region of the CIE chromaticity diagram. The present results indicate that PbO-GeO2 glass has large potential to be used for white displays.

Influence of silicon nanocrystals on the performance of Yb3+/Er3+: Bi2O3-GeO2 pedestal waveguides for amplification at 1542 nm

This paper reports for, the first time, the influence of silicon nanocrystals on the photoluminescence and optical gain of Yb3+/Er3+ codoped Bi2O3−GeO2 waveguides for amplification at 1542 nm. Pedestal waveguides were fabricated by RF- sputtering followed by optical lithography and reactive ion etching. RF-sputtering followed by heat treatment produced silicon nanocrystals with average size of 8 nm and resulted in a photoluminescence enhancement of about 10 times for the 520 nm and 1530 nm emission bands. The resulting internal gain was 5.5 dB/cm at 1542 nm, which represents and enhancement of ∼50%, demonstrating potential for applications in integrated optics.

Luminescence of Er3+ doped TeO2-ZnO glass containing silicon nanocrystals

We investigate the influence of silicon nanocystals on Er3+ doped TeO2-ZnO. Large enhancement of the photoluminescence is observed. This is the first observation of photoluminescence enhancement in Er3+ doped TeO2-ZnO composites due to silicon nanocrystals.