Luyun Yang

Ce-Tb-Mn co-doped white light emitting glasses suitable for long-wavelength UV excitation

We report on a new kind of white light emitting glass suitable for long-wavelength ultraviolet excitation by simultaneously emitting blue, green and red fluorescence, which is fabricated by melting of Ce(3+)-Tb(3+)-Mn(2+) co-doped borosilicate glass. The spectroscopic properties of singly, doubly and triply doped glasses have been reported and the energy transfer from Ce(3+) to Tb(3+) and Mn(2+) has also been investigated. By adjusting the concentration of different co-dopants, we obtained the ideal white light emitting borosilicate glass with the color coordinate (x = 0.318, y = 0.333).

Tailoring of clusters of active ions in sintered nanoporous silica glass for white light luminescence

To tailor clusters of active ions in glasses is laborious but critical for obtaining high efficient luminescence. Here, we present a facile method to tailor clusters of active ions by using one kind of porous host, the nanoporous silica glass. The white light-emitting glasses were prepared by sintering of nanoporous silica glasses impregnated with Ce3+, Tb3+, Mn2+ and Al3+ ions. The combination of blue, green and red emissions of Ce3+, Tb3+ and Mn2+ ions in the glasses under ultraviolet light excitation create white light emissions. The fluorescence of the glasses under long-wavelength ultraviolet excitation are dependent on energy transfer processes between the active ions; and the Al3+ plays a key role in adjusting of the energy transfer processes.

Enhanced green luminescence in Ce-Tb-Ca codoped sintered porous glass.

We report on a new kind of green-emitting high silica luminous glass, which is fabricated by sintering of Ce(3+)-Tb(3+) co-doped porous glass. The spectra show that there are energy transfer between Ce(3+) and Tb(3+), and cross-relaxation between (5)D(3) and (5)D(4) energy level of Tb(3+). The energy transfer process can be adjusted by addition of Ca(2+) into the Ce(3+)-Tb(3+) co-doped porous glass, and the transfer rate can be enhanced about four times than that of Ce(3+)-Tb(3+) co-doped porous glass. The role of Ca(2+) has been discussed, and the fluorescence decay curve reveals that the Ca(2+) play an important role in energy transfer.

Effect of Yb 3+ concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silica-based glasses

The effect of Yb(3+) concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silicate glasses is investigated. The optimal Bi(2)O(3) concentration range is about 2.0-2.5 mol% in 65SiO(2)-10Al(2)O(3)-25CaO matrix (SAC glasses). For Yb/Bi codoped SAC glasses, the maximum emission intensity excited by 980 nm LD is ~30 times and 1.5 times higher than that of single Bi-doped SAC glasses excited by 980 nm and 808 nm LD, respectively, the peak emission shows obvious red-shift from 1185 nm to 1235 nm band with the Yb(2)O(3) concentration change from 0 to 3.0 mol%. For the same Yb(2)O(3) concentration in SAC glasses, the measured fluorescence lifetime near 1020 nm of single Yb(3+)-doped glasses is longer than that of Yb/Bi codoping glasses, which implyes the efficient energy transfer from Yb(3+) to Bi(n+) in SAC glasses. The results indicate Yb(2)O(3) can be induced into the bismuth-doped silicate glasses to enhance the emission intensity and control the peak wavelength.

Investigation on radiation resistance of Er/Ce co-doped silicate glasses under 5 kGy gamma-ray irradiation

Various Er/Ce co-doped SiO2-Al2O3-CaO glasses are prepared by the melt-quenching method. The radiation resistance of Er/Ce co-doped glasses is investigated under 5 kGy gamma-ray irradiation. The absorption spectra, up-conversion spectra, fluorescence intensity and lifetime of Er/Ce co-doped glasses before and after irradiation are measured and analyzed in details. The radiation induced absorption (RIA) of the Er/Ce co-doped silicate glasses can be suppressed due to Ce ions co-doping. The fluorescence intensity and lifetime of Er/Ce co-doped glasses have no apparent change after irradiation. Furthermore, the possible mechanism of Ce effect on the radiation resistance improvement is discussed. The result indicates that Er doped glasses with an optimal Ce concentration introduction can be used as active medias for radiation-resistant materials in harsh radiation environments.

Effect of yttrium oxide addition on absorption and emission properties of bismuth-doped silicate glasses

Abstract Y/Bi co-doped silicate glasses were prepared, and the effects of Y 2 O 3 on the absorption and emission properties were investigated by spectrum measurement. It was found that the absorption intensity in visible region decreases with increase of Y 3+ concentration in (70– x )SiO 2 - x Y 2 O 3 -30CaO-1.5Bi 2 O 3 ( x =0 mol.%, 1 mol.%, 3 mol.%, 5 mol.%, 7 mol.%) glasses. The emissions centered at 410, 630, 1200 and 1290 nm were observed under 280, 470, 514 and 808 nm excitation, respectively. The emission intensity had the similar change tendency in the visible and near infrared region. We also discussed the actual role of Y 3+ ions playing in the visible and near infrared emissions of the silicate glasses.

Yb³⁺-doped large core silica fiber for fiber laser prepared by glass phase-separation technology.

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.

Mitigation of photodarkening effect in Yb-doped fiber through Na^+ ions doping

In this work, Na+ ions doping into the Yb-doped fiber is proposed to improve the photo-darkening resistance. The results show that the photo-darkening induced excess loss at equilibrium state at 633nm, 702 nm, 810 nm, and 1041 nm is 115.54dB/m, 86.87dB/m, 25.51 dB/m, 2.92 dB/m, respectively, when co-doping with Na+ ions. More than 30% excess loss is reduced comparing to the Yb-doped fiber without Na+ ions. The mechanism of Na+ ions doping to mitigate the PD excess loss is discussed. Besides, we measured the laser efficiency of Yb/Al/Na co-doped fiber to be 76.1%. This result remains almost the same with Yb-doped fiber and proves that the addition of Na+ ions do not deteriorate the fiber slope efficiency. The background loss of the two fibers also stays close. The results indicate this method is promising in high power fiber laser development.

Intense ultra-broadband down-conversion in co-doped oxide glass by multipolar interaction process.

We report that Eu(2+) can be an efficient sensitizer for Yb(3+) and a broadband absorber for blue solar spectra in the host of oxide glass. The greenish 4f → 5d transition of Eu(2+) and the characteristic near-infrared emission of Yb(3+) were observed, with the blue-light of xenon lamp excitation. The 5d energy can be adjusted by the host and the energy transfer efficiency can be enhanced. The quantum efficiency is up to 163.8%. Given the broad excitation band, high absorption coefficient and excellent mechanical, thermal and chemical stability, this system can be useful as down-conversion layer for solar cells.

Manufacturing a Long-Period Grating with Periodic Thermal Diffusion Technology on High-NA Fiber and Its Application as a High-Temperature Sensor

We demonstrated a kind of long-period fiber grating (LPFG), which is manufactured with a thermal diffusion treatment. The LPFG was inscribed on an ultrahigh-numerical-aperture (UHNA) fiber, highly doped with Ge and P, which was able to easily diffuse at high temperatures within a few seconds. We analyzed how the elements diffused at a high temperature over 1300 °C in the UHNA fiber. Then we developed a periodically heated technology with a CO2 laser, which was able to cause the diffusion of the elements to constitute the modulations of an LPFG. With this technology, there is little damage to the outer structure of the fiber, which is different from the traditional LPFG, as it is periodically tapered. Since the LPFG itself was manufactured under high temperature, it can withstand higher temperatures than traditional LPFGs. Furthermore, the LPFG presents a higher sensitivity to high temperature due to the large amount of Ge doping, which is approximately 100 pm/°C. In addition, the LPFG shows insensitivity to the changing of the environment’s refractive index and strain.