[en] The mid-infrared (MIR) luminescent properties of Dy³⁺ ions in a new chalcohalide glass host, Ga₂S₃–Sb₂S₃–CsI, are investigated; and the suitability of the doped glass for MIR fiber lasers is evaluated. The Dy³⁺-doped chalcohalide glasses exhibit good thermal stability and intense MIR emissions around 2.96 μm and 4.41 μm. These emissions show quantum efficiencies (η) as high as ∼ 60%, and have relatively large stimulated emission cross sections (σ _em). The low phonon energy (∼ 307 cm⁻¹) of the host glass accounts for the intense MIR emissions, as well as the high η. These favorable thermal and emission properties make the Dy³⁺-doped Ga₂S₃–Sb₂S₃–CsI glasses promising materials for MIR fiber amplifiers or lasers. (paper)

[en] A series of Er³⁺-doped (1 − x)CaF₂–xYbF₃ (0 ≤ x ≤ 0.6) disordered solid-solution nanocrystals with various mean sizes were successfully prepared by a facile solvothermal route. Interestingly, abnormal size-dependent upconversion emissions were demonstrated in these nanocrystals for the first time. With increasing grain size, an obvious enhancement of red to green emission ratio was observed in the Er³⁺ (2 mol%): 0.4CaF₂–0.6YbF₃ nanocrystals, which is the opposite of the routine size-dependent upconversion emission behavior reported previously. Taking Eu³⁺ ions as a structural probe, we investigated the influence of a disordered solid-solution structure on Ln³⁺ luminescence, and proposed that Ln³⁺ clusters formed in the host should play a key role to induce this unusual size-dependent upconversion emission phenomenon. As a consequence, multi-colors such as green, yellow, and red upconversion emissions can be easily realized by appropriately modifying the Yb³⁺ content in the Er³⁺-doped (1 − x)CaF₂–xYbF₃ nanocrystals. The reported results will deepen the understanding of size effects on the lanthanide upconversion in nanocrystals. (paper)

[en] Co²⁺/Er³⁺ co-doped transparent glass ceramic embedding spinel ZnAl₂O₄ and orthorhombic Y F₃ nanocrystals was fabricated successfully by a conventional melt-quenching method for the first time. The sequential precipitations of ZnAl₂O₄ and Y F₃ phases from the precursor glass are confirmed by x-ray diffraction and transmission electron microscopy. Spectroscopic results reveal that the selective incorporations of Co²⁺ and Er³⁺ ions into the ZnAl₂O₄ and Y F₃ nanocrystals respectively are achieved, leading to complete suppression of the energy transfer between Co²⁺ and Er³⁺. The investigated glass ceramic, in which the tetrahedrally coordinated Co²⁺ could create saturated absorption for the Er³⁺ emission at 1.54 μm, might find potential application as a self-Q-switched laser material. (paper)

[en] Eu³⁺ doped transparent glass ceramics embedding SnO₂ nano-crystals were prepared by melt quenching and subsequent heating. Site selective excitation experiments revealed that some Eu³⁺ ions were incorporated in the SnO₂ lattices by substituting Sn⁴⁺ ions, whereas the rest located in the oxide glassy matrix. Interestingly, it is found that the Eu³⁺ ions residing in the SnO₂ lattices exhibited much longer luminescent decay lifetime than those in the glassy matrix. Measurements on the photoluminescence excitation and photoluminescence spectra demonstrated the occurrence of energy transfer from the SnO₂ nano-crystals to the Eu³⁺ ions. The influences of Eu³⁺ content, and furthermore, their location on the energy transfer process were discussed. -- Graphical abstract: The Eu³⁺ distribution-related energy transfer behavior in transparent glass ceramics embedding SnO₂ nano-crystals. Display Omitted Research Highlights: →We prepared Eu³⁺ doped glass ceramics embedding SnO₂ nano-crystals by melt quenching. →The incorporation of Eu³⁺ in the SnO₂ lattices by substituting Sn⁴⁺ was revealed. →The efficient energy transfer from SnO₂ to Eu³⁺ was verified. →The Eu³⁺ distribution-related energy transfer behavior was proposed.

[en] Highlights: ► Ultraviolet upconversion emissions of Eu³⁺ and Gd³⁺ are rarely studied. ► Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. ► Ultraviolet upconversion signal are found greatly enhanced after crystallization. ► It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu³⁺ (⁵H_3–7, ⁵G_2–6, ⁵L₆ → ⁷F₀) and Gd³⁺ (⁶I_J, ⁶P_J → ⁸S_7/2) are studied in the Eu³⁺ (or Gd³⁺) doped SiO₂–Al₂O₃–NaF–YF₃ precursor glasses and glass ceramics containing β-YF₃ nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb³⁺ to Tm³⁺, then further to Eu³⁺ or Gd³⁺ is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of β-YF₃ nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.

[en] Research highlights: → Eu²⁺/Yb³⁺:CaF₂ nanocrystals embedded transparent glass ceramics are prepared. → Yb³⁺ downconversion emission occurs through energy transfer from Eu²⁺ to Yb³⁺. → Such material might be used to enhance the energy efficiency of Si solar cell. - Abstract: Cooperative downconversion was realized in glass ceramics containing Eu²⁺/Yb³⁺:CaF₂ nanocrystals with Eu²⁺ greatly absorbing ultraviolet photons. Upon excitation of Eu²⁺ ions to the 5d level with an ultraviolet photon at 320 nm, emission of two near infrared photons at 976 nm of Yb³⁺ were achieved. The dependence of the visible and near-infrared emissions, decay lifetime, and quantum efficiency on the Yb³⁺ doping content has been investigated. The maximum energy transfer efficiency and the corresponding downconversion quantum efficiency were estimated to be 51% and 151%, respectively.

[en] Highlights: • A new chalcogenide glass system Ga₂S₃-Sb₂S₃-La₂S₃ (GSLS) is developed. • A core/cladding fiber based on Dy³⁺-doped GSLS glass is fabricated. • The 20Ga₂S₃-75Sb₂S₃-5La₂S₃ glass has the best thermal stability. • The Dy³⁺-doped GSLS glass and fiber show intense mid-infrared emissions. • Fabricated fiber has a background loss of We report a new Dy³⁺-doped Ga₂S₃-Sb₂S₃-La₂S₃ (GSLS) chalcogenide glass for mid-infrared (mid-IR) laser applications. With the addition of La₂S₃ into the previously studied Ga₂S₃-Sb₂S₃ glass, the thermal stability of the base glass is significantly enhanced. The glass with the composition 20Ga₂S₃-75Sb₂S₃-5La₂S₃ (mol.%) shows the best thermal stability for fiber drawing, and the glass can be doped with up to 5 mol.% Dy₂S₃. The Dy³⁺-doped GSLS bulk glasses and a multimode fiber exhibit intense emissions at 2.95 μm and 4.40 μm. Spectroscopic analyses show that the mid-IR emissions are with high quantum efficiencies and large stimulated emission cross sections, indicating that Dy³⁺-doped GSLS glass is a promising candidate for mid-IR fiber laser medium.

[en] Graphical abstract: The phase-separation induced nucleation and growth of Cs₃LaCl₆ nanocrystals has been studied for the first time. It is experimentally evidenced that the doped active rare earth ions are incorporated into the Cs₃LaCl₆ nanocrystals, resulting in the intensified down- and up-conversion emissions. - Highlights: • A novel transparent glass ceramic containing Cs₃LaCl₆ nanocrystals was fabricated. • Crystallization behaviors of Cs₃LaCl₆ nanophase are systematically investigated. • The up-/down-conversion emissions are greatly intensified after crystallization. - Abstract: The phase-separation induced nucleation and growth of Cs₃LaCl₆ nanocrystals has been studied in the GeS₂-Ga₂S₃-La₂S₃-LaCl₃-CsCl system for the first time. Remarkably, the precipitated chloride nanocrystals are spherical and distributed homogeneously in the glass matrix. Benefiting from the uniform structure, high transparency of the glass ceramic is maintained after heat treatment by reducing adverse optical scattering. As revealed by the absorption spectra and Judd–Ofelt calculations, the doped active rare earth ions are partially partitioned into the low-phonon-energy Cs₃LaCl₆ nanocrystals, resulting in the decrease of the non-radiative transition probabilities and therefore intensified photoluminescence emission of Nd³⁺ and up-conversion one of Er³⁺

[en] Highlights: • Novel Ga–Sb–S chalcogenide glasses doped with Dy"3"+ ions were synthesized. • The glasses show good thermal stability and excellent infrared transparency. • The glasses show low phonon energy and intense mid-infrared emissions. • The mid-infrared emissions have high quantum efficiency. • The mid-infrared emissions have large stimulated emission cross sections. - Abstract: Novel Ga–Sb–S chalcogenide glasses doped with different amount of Dy"3"+ ions were prepared. Their thermal stability, optical properties, and mid-infrared (MIR) emission properties were investigated. The glasses show good thermal stability, excellent infrared transparency, very low phonon energy (∼306 cm"−"1), and intense emissions centered at 2.95, 3.59, 4.17 and 4.40 μm. Three Judd–Ofelt intensity parameters (Ω_2 = 8.51 × 10"−"2"0 cm"2, Ω_4 = 2.09 × 10"−"2"0 cm"2, and Ω_6 = 1.60 × 10"−"2"0 cm"2) are obtained, and the related radiative transition properties are evaluated. The high quantum efficiencies and large stimulated emission cross sections of the MIR emissions (88.10% and 1.11 × 10"−"2"0 cm"2 for 2.95 μm emission, 75.90% and 0.38 × 10"−"2"0 cm"2 for 4.40 μm emission, respectively) in the Dy"3"+-doped Ga–Sb–S glasses make them promising gain materials for the MIR lasers

[en] Although Ho³⁺ doped glasses and fibers lasing at 2.1 μm have been extensive studied, an effective means of power scaling still attracts interest from academic and industry societies. Here, by combining the unique characteristics of Bi₂O₃-B₂O₃-SiO₂ bismuthate glasses and oxidizing effect of CeO₂ doping, Ce³⁺/Yb³⁺/Ho³⁺ triply doped glasses of improved optical properties can be obtained. A dramatically enhanced (by more than 50%) 2.1 μm emission of Ho³⁺ is observed. The underlying mechanism and the possible energy transfer processes between Ce³⁺, Yb³⁺ and Ho³⁺ are discussed. The enhanced emission, together with a full width at half maximum of 190 nm, a stimulated emission cross-section of 4.1 × 10⁻²¹ cm² and an extremely large internal quantum efficiency (more than 90%) of the 2.1 μm emission of Ho³⁺, suggests good potential of the studied glasses for fiber amplifiers. - Highlights: • The emissions of Yb³⁺ and Ho³⁺ doped bismuthate glasses are greatly enhanced by CeO₂ doping. • The mechanism behind the enhanced emission of Yb³⁺ due to CeO₂ doping is established. • The relationship between the emissions of Yb³⁺ and Ho³⁺ is established.