Tunable Visible Light and Energy Transfer Mechanism in Tm3+ and Silver Nanoclusters within Co-Doped GeO2-PbO Glasses

This study introduces a novel method for producing Ag nanoclusters (NCs) within GeO2-PbO glasses doped with Tm3+ ions. Sample preparation involved the melt-quenching method, employing adequate heat treatment to facilitate Ag NC formation. Absorption spectroscopy confirmed trivalent rare-earth ion incorporation. Ag NC identification and the amorphous structure were observed using transmission electron microscopy. A tunable visible emission from blue to the yellow region was observed. The energy transfer mechanism from Ag NCs to Tm3+ ions was demonstrated by enhanced 800 nm emission under 380 and 400 nm excitations, mainly for samples with a higher concentration of Ag NCs; moreover, the long lifetime decrease of Ag NCs at 600 nm (excited at 380 and 400 nm) and the lifetime increase of Tm3+ ions at 800 nm (excitation of 405 nm) corroborated the energy transfer between those species. Therefore, we attribute this energy transfer mechanism to the decay processes from S1→T1 and T1→S0 levels of Ag NCs to the 3H4 level of Tm3+ ions serving as the primary path of energy transfer in this system. GeO2-PbO glasses demonstrated potential as materials to host Ag NCs with applications for photonics as solar cell coatings, wideband light sources, and continuous-wave tunable lasers in the visible spectrum, among others.

Silver Nanoclusters Tunable Visible Emission and Energy Transfer to Yb3+ Ions in Co-Doped GeO2-PbO Glasses for Photonic Applications

This work investigates the optical properties of Yb³⁺ ions doped GeO₂-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb³⁺ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb³⁺ ions (²F_7/2 → ²F_5/2) was attributed to the S₁→T₁ decay (spin-forbidden electronic transition between singlet-triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb³⁺ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb³⁺ ions to the growth of NCs is responsible for these effects. Thus, higher Yb³⁺ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb³⁺ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices.

Near-IR Luminescence of Rare-Earth Ions (Er3+, Pr3+, Ho3+, Tm3+) in Titanate-Germanate Glasses under Excitation of Yb3

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO₂-modified germanate glasses co-doped with Yb³⁺/Ln³⁺ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the ²F_7/2 → ²F_5/2 transition of Yb³⁺). We demonstrated that the introduction of TiO₂ is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr³⁺: ¹G₄ → ³H₅), 1.5 μm (Er³⁺: ⁴I_13/2 → ⁴I_15/2), 1.8 μm (Tm³⁺: ³F₄ → ³H₆) and 2.0 μm (Ho³⁺: ⁵I₇ → ⁷I₈). Based on the lifetime values, the energy transfer efficiencies (η_ET) were estimated. The values of η_ET are changed from 31% for Yb³⁺/Ho³⁺ glass to nearly 53% for Yb³⁺/Pr³⁺ glass. The investigations show that obtained titanate-germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range.

Net Optical Gain Coefficients of Cu+ and Tm3+ Single-Doped and Co-Doped Germanate Glasses

Broadband tunable solid-state lasers continue to present challenges to scientists today. The gain medium is significant for realizing broadband tunable solid-state lasers. In this investigation, the optical gain performance for Tm³⁺ and Cu⁺ single-doped and co-doped germanate glasses with broadband emissions was studied via an amplified spontaneous emission (ASE) technique. It was found that the net optical gain coefficients (NOGCs) of Tm³⁺ single-doped glass were larger than those for Cu⁺ single-doped glass. When Tm³⁺ was introduced, the emission broadband width of Cu⁺-doped glass was effectively extended. Moreover, it was found that for the co-doped glass the NOGCs at the wavelengths for Tm³⁺ and Cu⁺ emissions were larger than those of Tm³⁺ and Cu⁺ single-doped glasses at the same wavelengths. In addition, the NOGC values of Tm³⁺ and Cu⁺ co-doped germanate glasses were of the same order of magnitude, and were maintained in a stable range at different wavelengths. These results indicate that the Tm³⁺ and Cu⁺ co-doped glasses studied may be a good candidate medium for broadband tunable solid-state lasers.