Zhongmin Yang

Spectral properties and thermal stability of Er3+-doped oxyfluoride silicate glasses for broadband optical amplifier

Abstract Er 3+ -doped 50SiO 2 –(50− x )PbO– x PbF 2 glasses were prepared. The effect of PbF 2 content on refractive indices, densities, absorption spectra, the Judd–Ofelt parameters Ω t ( t =2,4,6), fluorescence spectra and the lifetimes of 4 I 13/2 level of Er 3+ in 50SiO 2 –(50− x )PbO– x PbF 2 glasses were investigated, and the stimulated emission cross-section was calculated from McCumber theory. With increasing PbF 2 content in the glass composition, the Ω 6 parameter, fluorescence full width at half maximum (FWHM) and lifetimes of 4 I 13/2 level of Er 3+ increase, while refractive indices and densities decrease. Compared with other glass hosts, the gain bandwidth properties of Er 3+ -doped 50SiO 2 –50PbF 2 glass is close to those of tellurite and bismuth glasses, and has an advantage over those of silicate, phosphate and germante glasses. The broad and flat 4 I 13/2 → 4 I 15/2 emission of Er 3+ around 1.55 μm can be used as host material for potential broadband optical amplifier in the wavelength–division–multiplexing (WDM) network system.

Thermal analysis and optical properties of Yb 3+ /Er 3+ -codoped oxyfluoride germanate glasses

Yb3+/Er3+-codoped Na2O–Al2O3–GeO2–PbO–PbF2 glasses that are suitable for use in fiber lasers, amplifiers, and waveguide devices have been fabricated and characterized. The density, refractive indices, optical absorptions, Judd–Ofelt parameters, and spontaneous-transition probabilities of the glasses have been measured and calculated. Intense and broad 1.53-μm infrared fluorescence and visible upconversion luminescence were observed under 976-nm diode laser excitation. For the 1.53-μm emission band, the full widths at the half-maximum increase and the peak wavelengths are blueshifted with an increase of PbF2. The stimulated-emission cross sections were calculated from the measured-absorption cross section according to the McCumber theory. The monotonically reduced emission cross section arises from the decreased refractive indices of glasses and the increased linewidth of the infrared fluorescence spectrum. For the upconversion emissions centered at 524, 547, and 660 nm, the emission intensity changes remarkably with PbF2 contents from 0 to 15 mol.%. The quadratic dependence of the green and red emissions on excitation power indicates that a two-photon absorption process occurs under the 976-nm excitation. The relatively long lifetimes of the Er3+ 4S3/2 and 4F9/2 levels for the NAGF3 glass gives rise to a much more intense upconversion emission.

The characteristics of granular-bright facet in hydrogen pre-charged and uncharged high strength steels in the very high cycle fatigue regime

In this study, the effect of hydrogen on fatigue strength of high strength steels in the very high cycle fatigue regime was further discussed. It is found that the calculated results of fatigue strength by modified Murakami’s expression are in good accordance with the experimental results in ±15% error band. The relationship between fatigue life (Nf) and the ratio of granular-bright facet (GBF) to inclusion size

Thermal stability and optical transition of Er3+ in sodium-lead-germanate glasses

\left({\frac{{\sqrt {A_{\text{GBF}} } }}{{\sqrt {A_{\text{inc}} } }}}\right)

Fluorescence quenching in Er3+ doped tellurite glass due to the introduction of BO3/2

for quenching and tempering (QT) specimens and pre-charged specimens by soaking (SK) and cathodic (CD) charging can be approximately expressed by

Prediction of the S-N curves of high-strength steels in the very high cycle fatigue regime

{\frac{{\sqrt {A_{\text{GBF}} } }}{{\sqrt {A_{\text{inc}} } }}} = {\frac{{R_{\text{GBF}} }}{{R_{\text{inc}} }}} = 0. 2 5N_{\text{f}}^{ 0. 1 2 5}