Dai Shi-Xun

Physical Properties of Novel Lead-Bismuthate Glasses with Large Transmitting Windows

Novel lead-bismuthate glasses with low OH concentration have been obtained in the Bi2O3–PbO–SrO system. The role of the different components in the glass formation has been explored from the density, refractive index measurements, indicating that the physical properties are mainly affected by Bi2O3 and PbO contents. The densities and refractive indices of these glasses are in the ranges of 7.639–7.699 g/cm3 and 2.47–2.94, respectively. A wide transmitting window from visible to infrared (IR) regions and good thermal stability for some compositions of these glasses have been observed, which make them appealing candidates for different optical applications such as upconverting phosphors, new laser materials, optical waveguides and crystal-free fibre drawing.

Frequency Upconversion Emission of Er3+-Doped Strontium?Lead?Bismuth Glasses

Er3+-doped strontium–lead–bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Under 975 nm excitation, intense green and red emissions centred at 525, 546, and 657 nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were observed at room temperature. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for 525 and 546 nm emissions, and energy transfer upconversion for 657 nm emission.

Multi-Rare-Earth Ions Codoped Tellurite Glasses for Potential Dual Wavelength Fibre-Optic Amplifiers

A novel co-doping method of multi-rare-earth (RE) ions was demonstrated in tellurite glasses for fibre amplifiers. Fluorescence emissions at both 1.53 and 1.63xa0µm communication windows were firstly observed from Er3+/Yb3+/Tm3+-codoped tellurite glasses under a single wavelength pumping at 980xa0nm. The full width at half maximum of fluorescence at 1.53 and 1.63xa0µm are 55xa0nm and 50xa0nm, respectively. This codoping method of three RE ions could be applied to other low photon energy glasses, which would be possibly used for potential dual wavelength fibre-optic amplifiers to broaden the communication windows.

Spectral Properties of Erbium-Doped Oxyfluoride Silicate Glasses for Broadband Optical Amplifiers

The new oxyfluoride silicate glasses of Er3+-doped 50SiO2-(50-x)PbO-xPbF2 were prepared. With increasing PbF2 content in the glass composition, the fluorescence full width at half maximum and lifetimes of the 4I13/2 level of Er3+ increase, while the refractive indices and densities decrease. Er3+-doped 50SiO2-50PbF2 glass showed broad fluorescence spectra of 1.55?mum with a large stimulated emission cross-section and long lifetimes of 4I13/2 level of Er3+. Compared with other glass hosts, the gain bandwidth properties of Er3+-doped 50SiO2-50PbF2 glass are close to those of tellurite and bismuth glasses, and have advantages over those of silicate, phosphate and germante glasses. The broad and flat 4I13/2?4I15/2 emission of Er3+ around 1.55??m can be used as host material for potential broadband optical amplifier in wavelength-division-multiplexing network system.

Blue Upconversion Luminescence in Tm3+/Yb3+-Codoped Lead Chloride Tellurite Glass

The thermal stability, Raman spectrum and upconversion properties of Tm^(3+)/Yb^(3+) co-doped new oxyfluoride tellurite glass are investigated. The results show that Tm^(3+)/Yb^(3+) co-doped oxyfluoride tellurite glass possesses good thermal stability, lower phonon energy, and intense upconversion blue luminescence. Under 980-nm laser diode (LD) excitation, the intense blue (475 nm) emission and weak red (649 nm) emission corresponding to the 1G4 -> 3H6 and 1G4 -> 3F4 transitions of Tm^(3+) ions respectively, were simultaneously observed at room temperature. The possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm^(3+)/Yb^(3+) co-doped oxyfluoride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.

Switching properties and phase transition mechanism of Mo6+-doped vanadium dioxide thin films

Using V2O5 and MoO3 powders as precursors, a novel preparation method, i.e., the so-called inorganic sol-gel, is developed to synthesize Mo6+-doped vanadium dioxide (VO2) thin films. The structure, valence state, phase transition temperature and magnitude of resistivity change are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and the four-point equipment. The results show that the main chemical composition of doped thin films was VO2, the structure of MoO3 in doped thin films did not change, and the phase transition temperature of doped thin films was obviously lowered with the increasing MoO3 doped concentration, but the magnitude of resistivity change was also decreased. However, so long as MoO3 doped concentration was not more than 5 wt.%, the magnitude of resistivity change of doped thin films still reached more 2 orders. The analysis show that MoO3 dissolved in crystal structure of VO2 formed the donor defect MOvx and then reduced the forbidden-band width, which lowered the phase transition temperature. Consequently it was widened applications of the VO2 thin films.

Mixed Former Effect: A Kind of Composition Adjusting Method of Er-Doped Glass for Broadband Amplification

A compositional adjusting method called the mixed former effect is proposed to improve effectively optical properties such as the emission cross section, the fluorescence full width at half maximum (FWHM) and the lifetime of the 4I13/2 level of Er-doped glass. A kind of Er-doped bismuth-based glass illustrated high emission cross section (σep = 0.66-0.90 pm2), large fluorescence FWHM (68-85 nm), and relatively long lifetime of the 4I13/2 level (τm = 1.6-4.3 ms) using this method. A comparison of spectroscopic parameters shows that bismuth-based glass is much better for broadband amplifiers than other glass hosts.

Infrared-to-green upconversion luminescence and mechanism of Ho^3＋, Nd^3＋ and Yb^3＋ ions in oxyfluoride glass ceramics

New oxyfluoride glasses and glass ceramics co-doped with Nd3+, Yb3+ and Ho3+ were prepared. The upconversion of infrared radiation into green fluorescence has been studied for Nd3+, Yb3+ and Ho3+ in the transparent oxyfluoride glass ceramics. At room temperature very strong green upconversion luminescence due to the Ho3+: (5F4, 5S2)→5I8 transition under 800 nm excitation was observed in the glass ceramics. The intensity of the green upconversion luminescence in a 1mol% YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ upconversion luminescence in the oxyfluoride glass ceramics is discussed. The upconversion mechanism is also investigated.

Effect of B2O3 on Judd-Ofelt parameters of Er3+-doped tellurite glasses

We have prepared Er3+-doped borotellurite glasses using conventional melting and quenching method. The absorption spectrum analysis is performed on the basis of Judd-Ofelt theory. The effects of B2O3 on the spectroscopic parameters such as intensity parameters, line strengths of electric-dipole transitions and spontaneous emission probability are discussed.

The effect of OH~- groups on the spectroscopic properties of erbium-doped tellurite glasses

A series of five different concentration erbium-doped tellurite glasses with various hydroxl groups were prepared. Infrared spectra of glasses were measured. In order to estimate the exact content of OH− groups in samples, various absorption coefficients of the OH− vibration band were analyzed under the different oxygen bubbling times. The absorption spectra of the glasses were measured, and the Judd-Ofelt intensity parameters Ω i of samples with the different erbium ions concentration and OH− contents were calculated on the basis of the Judd-Ofelt theory. The peak stimulated emission cross-section of 4|13/2→4|15/2 transition of the samples was finally calculated by using the McCumber theory. The fluorescence spectra of Er3+:4|13/2→4|15/2 transition and the lifetime of Er3+:4|13/2 level of the samples were measured. The effects of OH− groups on the spectroscopic properties of Er3+ doped samples with the different concentrations were discussed. The results showed that the OH− groups had great influences on the Er3+ lifetime and the fluorescence peak intensity. The OH− group is a main influence factor of fluorescence quenching when the doping concentration of Er2O3 is smaller than 1.0 mol%, but higher after this concentration, the energy transfer of Er3+ ions turns into the main function of the fluorescence quenching. And basically, there is no influence on the other spectroscopic properties (FWHM, absorption spectra, peak stimulated emission cross section, etc.).A series of five different concentration erbium-doped tellurite glasses with various hydroxl groups were prepared. Infrared spectra of glasses were measured. In order to estimate the exact content of OH− groups in samples, various absorption coefficients of the OH− vibration band were analyzed under the different oxygen bubbling times. The absorption spectra of the glasses were measured, and the Judd-Ofelt intensity parameters Ωi of samples with the different erbium ions concentration and OH− contents were calculated on the basis of the Judd-Ofelt theory. The peak stimulated emission cross-section of 4|13/2→4|15/2 transition of the samples was finally calculated by using the McCumber theory. The fluorescence spectra of Er3+:4|13/2→4|15/2 transition and the lifetime of Er3+:4|13/2 level of the samples were measured. The effects of OH− groups on the spectroscopic properties of Er3+ doped samples with the different concentrations were discussed. The results showed that the OH− groups had great influences on the Er3+ lifetime and the fluorescence peak intensity. The OH− group is a main influence factor of fluorescence quenching when the doping concentration of Er2O3 is smaller than 1.0 mol%, but higher after this concentration, the energy transfer of Er3+ ions turns into the main function of the fluorescence quenching. And basically, there is no influence on the other spectroscopic properties (FWHM, absorption spectra, peak stimulated emission cross section, etc.).