Muzhi Cai

Mid-infrared fluorescence, energy transfer process and rate equation analysis in Er3+ doped germanate glass

Er3+ doped Y2O3 and Nb2O5 modified germanate glasses with different Er3+ concentrations were prepared. J-O intensity parameters were computed to estimate the structural changes due to the additions of Y2O3 and Nb2O5. The main mid-infrared spectroscopic features were investigated. To shed light on the observed mid-infrared radiative behavior, 975 nm and 1.53 μm emission spectra along with their decay lifetimes were also discussed. Moreover, the energy transfer processes of 4I11/2 and 4I13/2 level were quantitatively analyzed. In view of the experimental lifetimes, the simplified rate equation was utilized to calculate the energy transfer upconversion processes of upper and lower laser level of 2.7 μm emission. The theoretical calculations are in good agreement with the observed 2.7 μm fluorescence phenomena. Finally, the stimulated emission and gain cross sections were calculated and the results indicate that Er3+ doped germanate glasses have great potential for mid-infrared application.

Quantitative Analysis of Energy Transfer and Origin of Quenching in Er3+/Ho3+ Codoped Germanosilicate Glasses

The energy transfer mechanism between Ho(3+) and Er(3+) ions has been investigated in germanosilicate glass excited by 980 nm laser diode. A rate equation model was developed to demonstrate the energy transfer from Er(3+) to Ho(3+) ions, quantitatively. Energy transfer efficiency from the Er(3+):(4)I13/2 to the Ho(3+):(5)I7 level can reach as high as 75%. Such a high efficiency was attributed to the excellent matching of the host phonon energy with the energy gap between Er(3+):(4)I13/2 and Ho(3+):(5)I7 levels. In addition, the energy transfer microparameter (CDA) from Er(3+):(4)I13/2 to Ho(3+):(5)I7 level was estimated to (4.16 ± 0.03) × 10(-40) cm(6)·s(-1) via the host-assisted spectral overlap function, coinciding with the CDA (2,88 ± 0.04) × 10(-40) cm(6)·s(-1) from decay analysis of the Er(3+):(4)I13/2 level which also indicated hopping migration-assisted energy transfer. Furthermore, the concentration quenching of Ho(3+):(5)I7 → (5)I8 transition was the dipole-dipole interaction in the diffusion-limited regime, and the quenching concentration of Ho(3+) reached 4.13 × 10(20) cm(-3).

Highly efficient mid-infrared 2 μm emission in Ho 3+ /Yb 3+ -codoped germanate glass

This work reports the mid-infrared emission properties around 2 μm in Ho3+/Yb3+ codoped germanate glasses. The glass not only possesses good chemical durability and good thermal stability but also has high mid-infrared transmittance around 2 μm (90%). In addition, the glass possesses considerably low OH− content (20.45 ppm) and large spontaneous transition probability (103.38 s−1) corresponding to the Ho3+:5I7→5I8 transition. Moreover, the measured lifetime of Ho3+:5I7 level is as high as 7.68 ms, and the quantum efficiency at 2 μm can reach 79.4%. The energy transfer processes of Yb3+:2F5/2 level and Ho3+:5I6 level were quantitatively analyzed according to the rate equation. Results indicate that the prepared germanate glass is a promising candidate for 2 μm mid-infrared laser materials applications.

Ho 3+ /Yb 3+ codoped silicate glasses for 2 μm emission performances

This paper discuss a series of Ho³⁺/Yb³⁺ codoped silicate glasses prepared by the melting method. 2 μm emissions of the samples are observed under the pump of 980 nm LD. The Judd-Ofelt parameters (Ω(λ)) and radiative properties are calculated and analyzed; the spontaneous transition probability can reach 78.71  s⁻¹. From the fluorescence spectra, the peak absorption and emission cross section of Ho³⁺ are 2.36×10⁻²¹ and 5.05×10⁻²¹ cm², respectively. In addition, we analyze the energy transfer process of Yb³⁺:  ²F(5/2) level to Ho³⁺:  ⁵I₆ level. Considering the luminance properties and good thermal property, we indicate that Ho³⁺/Yb³⁺ codoped silicate glass is a potential laser glass for the efficient 2 μm laser.

R2O3 (R = La, Y) modified erbium activated germanate glasses for mid-infrared 2.7 μm laser materials

Er3+ activated germanate glasses modified by La2O3 and Y2O3 with good thermal stability were prepared. 2.7 μm fluorescence was observed and corresponding radiative properties were investigated. A detailed discussion of J–O parameters has been carried out based on absorption spectra and Judd–Ofelt theory. The peak emission cross sections of La2O3 and Y2O3 modified germanate glass are (14.3 ± 0.10) × 10−21 cm2 and (15.4 ± 0.10) × 10−21 cm2, respectively. Non-radiative relaxation rate constants and energy transfer coefficients of 4I11/2 and 4I13/2 levels have been obtained and discussed to understand the 2.7 μm fluorescence behavior. Moreover, the energy transfer processes of 4I11/2 and 4I13/2 level were quantitatively analyzed according to Dexter’s theory and Inokuti–Hirayama model. The theoretical calculations are in good agreement with the observed 2.7 μm fluorescence phenomena. Results demonstrate that the Y2O3 modified germanate glass, which possesses more excellent spectroscopic properties than La2O3 modified germanate glass, might be an attractive candidate for mid-infrared laser.

Enhancement of 1.53 μm emission in erbium/cerium-doped germanosilicate glass pumped by common 808 nm laser diode.

Erbium-doped germanosilicate glasses with various cerium ions contents have been prepared. Optical absorption and 1.53 μm emission spectra were measured to characterize the spectroscopic performances of prepared samples. A detailed study of 1.53 μm spectroscopic properties was carried out when pumped by an 808 nm laser diode. Moreover, an energy level diagram and an energy transfer mechanism between Er3+ and Ce3+ were proposed to elucidate the enhanced 1.53 μm fluorescence. It is found that the prepared samples have optimal spectroscopic properties when the Ce3+ concentration is fixed to 0.5 mol. %. High spontaneous radiative transition probability (172.66  s(-1)), large effective emission bandwidth (74 nm), and emission cross section (9.49×10(-21)  cm(2) indicate that 808 nm pumped Er3+/Ce3+ codoped germanosilicate glass might be a suitable material for a broadband optical amplifier.

The influence of TeO2 on thermal stability and 1.53 μm spectroscopic properties in Er3+ doped oxyfluorite glasses

In this work, the thermal and spectroscopic properties of Er(3+)-doped oxyfluorite glass based on AMCSBYT (AlF3-MgF2-CaF2-SrF2-BaF2-YF3-TeO2) system for different TeO2 concentrations from 6 to 21 mol% is reported. After adding a suitable content of TeO2, the thermal ability of glass improves significantly whose ΔT and S can reach to 118 °C and 4.47, respectively. The stimulated emission cross-section reaches to 7.80×10(-21) cm(2) and the fluorescence lifetime is 12.18 ms. At the same time, the bandwidth characteristics reach to 46.41×10(-21) cm(2) nm and the gain performance is 63.73×10(-21) cm(2) ms. These results show that the optical performances of this oxyfluorite glass are very well. Hence, AMCSBYT glass with superior performances might be a useful material for applications in optical amplifier around 1.53 μm.

Tm 3+ -doped lead silicate glass sensitized by Er 3+ for efficient ~2 μm mid-infrared laser material

Er3+/Tm3+ co-doped lead silicate glasses with low phonon (953cm-1) and good thermal stability were synthesized. The ~2μm mid-infrared emission resulting from the 3F4→3H6 transition of Tm3+ sensitized by Er3+ has been observed by 808nm LD pumping. The optimal luminescence intensity was obtained in the sample with 1Tm2O3/2.5Er2O3 co-doped. Moreover, the energy transfer mechanism from Er3+ to Tm3+ ion was analyzed. Absorption and emission cross section have been calculated. The calculated maximum emission cross section of Tm3+ is 2.689×10-21cm2 at 1863nm. Microparameters of energy transfer between Er3+ and Tm3+ ions have also been analyzed. These results ensure that the prepared Er3+/Tm3+ co-doped lead silicate glasses have excellent spectroscopic properties in mid-infrared region and provide a beneficial guide for mid-infrared laser material.

Mid-infrared emission and quantitative analysis of energy transfer processes in Er3+ doped oxyfluogermanate glasses

Oxyfluogermanate glasses with good thermal stability were prepared by melt-quenching method. The investigation of 2.7 μm fluorescence spectra and energy transfer mechanism was performed pumped by an 808 nm laser diode. The 2.7 μm radiative transition probability and emission cross section are 32.62 s−1 and 12.88 × 10−21 cm2, respectively. The energy transfer parameters between 4I11/2 and 4I13/2 levels were calculated by Inokuti-Hirayama and Yokota-Tanimotos model to further elucidate 2.7 μm fluorescent behaviors. It is found that the energy transfer mechanism among Er3+ is mainly dominated by dipole-dipole interactions. Results indicate that the prepared oxyfluogermanate glass is a promising candidate for mid-infrared laser applications.

Mid-infrared emission and Raman spectra analysis of Er 3+ -doped oxyfluorotellurite glasses

This paper reports on the spectroscopic and structural properties in Er(3+)-doped oxyfluorotellurite glasses. The compositional variation accounts for the evolutions of Raman spectra, Judd-Ofelt parameters, radiative properties, and fluorescent emission. It is found that, when maximum phonon energy changes slightly, phonon density plays a crucial role in quenching the 2.7 μm emission generated by the Er(3+):(4)I11/2→(4)I13/2 transition. The comparative low phonon density contributes strong 2.7 μm emission intensity. The high branching ratio (18.63%) and large emission cross section (0.95×10(-20)  cm(2)) demonstrate that oxyfluorotellurite glass contained with 50 mol.% TeO2 has potential application in the mid-infrared region laser.