Nengli Dai

Effect of Bi 2 O 3 on the spectroscopic properties of erbium-doped bismuth silicate glasses

The spectroscopic properties of erbium-doped silicon dioxide, bismuth oxide, and sodium oxide glasses are investigated based on Judd–Ofelt analysis for absorption spectra, bandwidth analysis for emission spectra, and lifetime measurements of the 4I13/2 level of Er3+. The effects of bismuth oxide on these three optical parameters are discussed in terms of the local basic nature of the glass, of variations in ligand fields about Er3+ sites, and of the phonon energy and the refractive index of the glass host, respectively. The data obtained suggest that bismuth oxide does not have a promising composition for use with a broadband erbium-doped fiber amplifier.

Investigation on nonradiative decay of 4I13/2→-4I15/2 transition of Er3+-doped oxide glasses

Abstract Nonradiative decay of 4 I 13/2 → 4 I 15/2 transition of Er 3+ has been investigated in a series of oxide glasses. For Er 3+ -doped glass samples, the Judd–Ofelt analysis on absorption spectra was performed and the fluorescence lifetime was determined by extrapolating to zero Er 3+ concentration limit. Infrared spectra were measured in order to investigate the influence of OH − groups in different glasses. The effects of glass matrix on the decay rate were discussed from the viewpoint of phonon energy, variations of effective fields, and OH − groups. Compared to other glasses, phosphate glass presents low quantum efficiency and large nonradiative decay rate due to its high phonon energy and hygroscopic behavior.

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).

Fabrication of ferroelectric PbZr0.4Ti0.6O3 multilayers by sol–gel process

Quasiperiodic ferroelectric PbZr0.4Ti0.6O3 multilayers have been fabricated using the sol–gel technique based on one single precursor. The building block of the multilayer is the distinct PbZr0.4Ti0.6O3/porous-PbZr0.4Ti0.6O3 bilayer formed in a single spin-casting/annealing step and the formation of the bilayer is governed by phase segregation process. The quasiperiodic ferroelectric multilayer exhibits good performance as a Bragg reflector. With 11 periods, 90% reflectivity and 40-nm stop-band width have been achieved at room temperature.

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.

Ba0.9Sr0.1TiO3-based Bragg reflectors fabricated from one single chemical solution

Periodic ferroelectric multilayers consisting of alternating stack of the dense and porous Ba0.9Sr0.1TiO3 layers have been fabricated by spin-coating and annealing sol-gel techniques using one single precursor. With 16 periods, the Ba0.9Sr0.1TiO3 multilayers exhibit excellent performance as dielectric mirrors: symmetric peak reflectivities of above 95% and flattopped stop bands of about 75nm. The reflectance peak position is tunable through varying the spinning rate in the spin-coating process. The lead-free Ba0.9Sr0.1TiO3 multilayers show high stability.

Spectroscopic properties of Yb3+-doped silicate glasses

Abstract The absorption, emission and potential laser properties of silicate glasses doped with Yb 3+ ions are investigated in detail. The emission cross-sections ( σ emi ) are calculated on the basis of reciprocity method according to the measured absorption spectra. The potential laser properties for Yb 3+ -doped glasses are evaluated by the minimum fraction of Yb 3+ ( β min ), the pump saturation intensity ( I sat ), the minimum pump intensity ( I min ), and the product of emission cross-section ( σ emi ) and fluorescence lifetime ( τ f ). The σ emi near 1020 nm and τ f of Yb 3+ in 61SiO 2 –25PbO–6Na 2 O–8K 2 O glass are 0.49 pm 2 and 2.00 ms, respectively, which are comparable to those in phosphate glasses. Systematical factor of laser properties (SFL) is introduced to evaluate the potential laser properties of Yb 3+ -doped glasses, the results indicate that Yb 3+ -doped silicate glasses are potential materials for double cladding ytterbium fiber laser application.

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.

Broadband Polarizers Using Dual-Layer Metallic Nanowire Grids

Broadband polarizers functioning in an extremely wide wavelength range from 0.3 to 5 mum were developed based on structural design and numerical simulation. By properly selecting the dual-layer nanowire grids including metal materials, grid periods, grid thicknesses, and substrate materials, broadband polarizers could be developed to realize high optical performance. We proposed a broadband polarizer using aluminum nanowire grids on a magnesium fluoride substrate with 80-nm square grids. The proposed polarizer can reach an extinction ratio from 47 to 70 dB and a transmission efficiency from 38% to 94% in the wide wavelength range.