White light emission and color tunability of dysprosium doped barium silicate glasses

Single crystals of the ABO3 phases CaTiO3, SrTiO3, BaTiO3, LiNbO3, KNbO3, LiTaO3, and KTaO3 were irradiated by 800 keV Kr+, Xe+, or Ne+ ions over the temperature range from 20 to 1100 K. The critical amorphization temperature, Tc, above which radiation-induced amorphization does not occur varied from approximately ∼450 K for the titanate compositions to more than 850 K for the tantalates. While the absolute ranking of increasing critical amorphization temperatures could not be explained by any simple physical parameter associated with the ABO3 oxides, within each chemical group defined by the B-site cation (i.e., within the titanates, niobates, and tantalates), Tc tends to increase with increasing mass of the A-site cation. Tc was lower for the Ne+ irradiations as compared to Kr+, but it was approximately the same for the irradiations with Kr+ or Xe+. Thermal recrystallization experiments were performed on the ion-beam-amorphized thin sections in situ in the transmission electron microscope (TEM). In the high vacuum environment of the microscope, the titanates recrystallized epitaxially from the thick areas of the TEM specimens at temperatures of 800–850 K. The niobates and tantalates did not recrystallize epitaxially, but instead, new crystals nucleated and grew in the amorphous region in the temperature range 825–925 K. These new crystallites apparently retain some `memory' of the original crystal orientation prior to ion-beam amorphization.

Amorphization and Recrystallization of the ABO3Oxides

Single-composition (or single-phase) phosphors have been proposed as a new strategy to overcome the concerns of emission reabsorption and different degradation rates of the three primary phosphors for light-emitting diode (LED) applications. A series of Ce3+, Sm3+ and Tb3+ co-doped NaSrBO3 phosphors were synthesized via a high temperature solid-state reaction. Upon near ultraviolet (NUV) excitation, tunable emission from violet to white in the visible region was realized in NaSrBO3:Ce3+,Sm3+,Tb3+ phosphors by controlling the dopant concentrations. Particularly, highly efficient white-light emission with a quantum yield as high as 48.2% was achieved. The energy transfer mechanism between Ce3+ and Sm3+ ions in NaSrBO3 was found to be predominantly of dipole–dipole nature. Moreover, the thermal quenching effect on the photoluminescence of NaSrBO3:Ce3+,Sm3+,Tb3+ was comprehensively surveyed over the range of 300–600 K, showing a good thermal stability for LED applications. By integrating this single-composition white-emitting NaSrBO3:Ce3+,Sm3+,Tb3+ phosphor with a 360 nm NUV chip, we fabricated a high-performance white LED (WLED), which exhibited an excellent color rendering index Ra of 80.1 and a correlated color temperature of 6731 K with CIE coordinates of (0.311, 0.314). These findings demonstrate that the proposed single-composition white-emitting NaSrBO3:Ce3+,Sm3+,Tb3+ phosphors can serve as promising phosphors for NUV-excited WLEDs.

Single-composition white-emitting NaSrBO3:Ce3+,Sm3+,Tb3+ phosphors for NUV light-emitting diodes

Quaternary alkaline earth zinc-phosphate glasses in molar composition (40 − x)ZnO – 35P2O5 – 20RO – 5TiO2 – xEu2O3 (where x=1 and R=Mg, Ca, Sr, and Ba) were prepared by melt quenching technique. These glasses were studied with respect to their thermal, structural, and photoluminescent properties. The maximum value of the glass transition temperature (Tg) was observed for BaO network modifier mixed glass and minimum was observed for MgO network modifier glass. All the glasses were found to be amorphous in nature. The FT-IR suggested the glasses to be in pyrophosphate structure, which matches with the theoretical estimation of O/P atomic ratio and the maximum depolymerization was observed for glass mixed with BaO network modifier. The intense emission peak was observed at 613 nm (5D0→7F2) under excitation of 392 nm, which matches well with excitation of commercial n-UV LED chips. The highest emission intensity and quantum efficiency was observed for the glass mixed with BaO network modifier. Based on these results, another set of glass samples was prepared with molar composition (40 − x)ZnO – 35P2O5 – 20BaO – 5TiO2 – xEu2O3 (x=3, 5, 7, and 9) to investigate the optimized emission intensity in these glasses. The glasses exhibited crystalline features along with amorphous nature and a drastic variation in asymmetric ratio at higher concentration (7 and 9 mol%) of Eu2O3. The color of emission also shifted from red to reddish orange with increase in the concentration of Eu2O3. These glasses are potential candidates to use as a red photoluminsecent component in the field of solid-state lighting devices.

Structural and emission properties of Eu3+-doped alkaline earth zinc-phosphate glasses for white LED applications

Bismuthene, as a novel two-dimensional (2D) material, has attracted extensive attention because of its outstanding properties including narrow band gap, stability at room temperature, nonlinear optical transmission, and so on. In this paper, the physical characteristic, nonlinear optical response, and ultrafast photonics application of few-layer bismuthene are studied experimentally. By the balanced twin-detector measurement method, the saturable absorption property of few-layer bismuthene with a modulation depth of 2.5% and saturable intensity of 110 MW/cm2 at the optical communication band (C-band) is illustrated. Dependent on a few-layer bismuthene saturable absorber, an all-fiber ultrashort pulse laser is fabricated and the proposed fiber laser can operate with coexistence of harmonic mode-locking and dual-wavelength mode-locking. The different laser generations of harmonic and dual wavelength depend on the saturable absorption of few-layer bismuthene, the suitable birefringence and nonlinearity strength in the laser cavity. The results suggest that the ultrashort pulse laser obtained based on few-layer bismuthene could be applied to the field of pump-probe experiments and tunable terahertz radiation generation potentially.

Few-Layer Bismuthene for Coexistence of Harmonic and Dual Wavelength in a Mode-Locked Fiber Laser

Efficient near-infrared quantum cutting in Ce3+–Yb3+ codoped glass for solar photovoltaic

We report on the preparation and optical characteristics of an Yb(3+)-doped large core silica fiber with the active core prepared from nanoporous silica rod by the glass phase-separation technology. The measurements show that the fiber has an Yb(3+) concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb(3+) about 5.5 dB/m at 976 nm. The laser performance presents a high slope efficiency of 72.8% for laser emission at 1071 nm and a low laser threshold of 3 W within only 2.3 m fiber length. It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs.

Yb 3+ -doped large core silica fiber for fiber laser prepared by glass phase-separation technology

We report on a kind of Ce3+/Tb3+/Sm3+ co-doped borosilicate glasses which can emit white light luminescence combined with red, green and blue fluorescence. In this manuscript, the energy transfer mechanism between Ce3+ and Tb3+ ions, Ce3+ and Sm3+ ions, and Tb3+ and Sm3+ ions is discussed by analysis of the steady and transient luminescence spectra of the doped ions. Based on the energy transfer mechanism, the near-ideal white light emission from the Ce3+/Tb3+/Sm3+ co-doped glasses with the color coordinate (x=0.335, y=0.337) has been observed under 350-nm excitation. Meanwhile, the calculated parameters such as color rendering index (78–81) and color temperature (4717–5372 K), characterizing luminous properties, show that the glasses can be potential candidates for displays and lighting.

White light luminous properties and energy transfer mechanism of rare earth ions in Ce 3+ /Tb 3+ /Sm 3+ co-doped glasses

Recent advances in high-power fiber lasers have imposed several pairs of higher requirements on fiber materials, such as larger fiber core/higher homogeneity and higher doping level/lower numerical...

3D Nanoporous Silica Rods for Extra-Large-Core High-Power Fiber Lasers

We report on a new kind of green-emitting (543 nm) high-silica luminous glass, which is fabricated by sintering of Yb3+–Tb3+ co-doped nanoporous glass. The fluorescence spectra show that there is an energy transfer between Yb3+ and Tb3+. The energy transfer process can be enhanced by addition of Al3+ into the Yb3+–Tb3+ co-doped nanoporous glass, and the energy transfer rate can be enhanced more than three times than that of Yb3+–Tb3+ co-doped porous glass. The role of Al3+ has been discussed, and the fluorescence decay curve reveals that the Al3+ play an important role in the energy transfer process.

Yingbo Chu

Papers

Efficient near-infrared quantum cutting in Ce3+–Yb3+ codoped glass for solar photovoltaic

Yb 3+ -doped large core silica fiber for fiber laser prepared by glass phase-separation technology

White light luminous properties and energy transfer mechanism of rare earth ions in Ce 3+ /Tb 3+ /Sm 3+ co-doped glasses

3D Nanoporous Silica Rods for Extra-Large-Core High-Power Fiber Lasers

Enhanced green upconversion luminescence in Yb–Tb co-doped sintered silica nanoporous glass