Search

Mid‐infrared (MIR) fiber lasers have wide application prospects and great commercial value in the fields of medical operation, remote sensing and military weapon, etc. At present, Tm3+‐doped glass can obtain broadband luminescence at 2 μm, the introduction of Ho3+ or Er3+ ions also shows a tunable MIR emission but with limited success. Herein, the rare‐earth (RE) doped glass with quantum dots (QDs) precipitation is proposed for achieving ultra‐broadband MIR emissions. The types and sizes of QDs are determined by the XRD and TEM, and their optical properties are further characterized by the absorption and emission spectra as well as the lifetime decay curves. It is found that the diameter of the QDs is gradually increased from 1.7 to 5.1 nm by increasing the heat‐treated temperature from 490°C to 530°C, respectively. Interestingly, an ultra‐broadband emission covering 1400‐2600 nm is achieved from the heat‐treated glass upon the excitation of 808 nm laser diode as a result of an overlapped emission from Tm3+ and PbS. All results suggest that these QDs‐precipitated RE‐doped glasses have important application prospects in ultra‐broadband MIR laser glass, glass fiber, and fiber lasers. [ABSTRACT FROM AUTHOR]

Abstract: Emission properties were investigated in the infrared region for Ga2S3-GeS2-Sb2S3 glasses doped with Ho3+. We performed Judd–Ofelt analysis and lifetime measurements of the 5 I 4, 5 I 5, and 5 I 6 levels, which are the initial levels of the mid-infrared emissions between 3 to 5μm of Ho3+. The quantum efficiencies reached approximately 18%, 64%, and ∼100% for the 5 I 4, 5 I 5, and 5 I 6, respectively. Population analyses were carried out from the relative intensities of the emissions in the near-infrared region. We investigated the dependences on the Ho3+ ion concentration of the population ratio of the initial levels to the final levels, [initial]/[final], of the mid-infrared emissions. The population ratio of [5 I 5]/[5 I 6] decreased with increase of the Ho3+ concentration while those of [5 I 4]/[5 I 5] and [5 I 6]/[5 I 7] increased. Particularly, the former, [5 I 4]/[5 I 5], rapidly increased because of the strong concentration quenching of the 5 I 5 level through cross relaxation. It was found that the population inversion for the 4.8μm emission due to the transition, 5 I 4→5 I 5, was achieved at high Ho3+ concentration in the present experiments. [Copyright &y& Elsevier]

Rare-earth ions doped fiber lasers at 2 µm can supply various applications in daily life. In this paper, Ho3+/Yb3+ co-doped tellurite glasses were prepared by the high temperature melting method to obtain a strong 2 µm mid-infrared fluorescence emission. The characterization results of the X-ray diffraction (XRD) and differential scanning calorimeter (DSC) show that this glass possesses good crystallization resistance and thermal stability, and its ΔT is 136 °C, which can be successfully drawn. Under the 980 nm LD excitation, strong green (550 nm) and red (660 nm) up-conversion emission were obtained, meanwhile, intensive 2 µm mid-infrared emission was also achieved, and the emission intensity was significantly improved with the increase of Yb3+ concentration, when the Yb3+ content was 2.0, the 2 µm mid-infrared emission intensity was increased by about 28% compared with the content of 0.5, it should be noted that the concentration of Yb3+ is required to be strictly controlled to prevent concentration quenching. In addition, the luminescence process of Ho3+ was further elaborated through the energy transfer mechanism. All results indicate that the Ho3+/Yb3+ co-doped tellurite glass can be an attractive candidate for up-conversion and mid-infrared fiber laser materials. [ABSTRACT FROM AUTHOR]

Under 635 nm laser excitation, the 3.5 μm luminescence, corresponding to the Er3+: 4F 9/2 → 4I 9/2 radiation transition, was demonstrated in Er3+ doped fluoroindate glasses prepared by melt-quenching method. The energy transfer mechanisms were investigated and the 3.5 μm emission intensity reached a maximum for an Er3+ concentration of 9 mol%. The Er3+ energy level lifetimes in fluoroindate glass samples were measured, their oscillator strength parameters were calculated by Judd-Ofelt theory and their emission cross-section at 3.5 μm was obtained. The maximum emission cross-section at 3.51 μm was 4.86 × 10−22 cm2, which indicated that Er3+ doped fluoroindate glass is a potential gain medium for lasing at 3.5 μm. • The absorption coefficient of OH− in galss sample is about 0.0011 cm−1. • The luminescence performance at λ~3.5 μm in Er3+ doped fluoroindate glass samples is investigated. • The maximum emission cross-section of 4.86 × 10−22 cm2 was obtained. [ABSTRACT FROM AUTHOR]

Broadband mid-infrared luminescence in Dy3+/Er3+ co-doped tellurite glasses was reported in this work. The doped tellurite glasses were prepared using conventional melt-quenching technique, and their structural property and thermal stability were analyzed by the X-ray diffraction (XRD) pattern, Raman spectrum and differential scanning calorimeter (DSC) curve. Judd-Ofelt theory was applied to the absorption spectra to evaluate the spectroscopic properties like radiative transition probability, branching ratio and radiative lifetime of Dy3+ and Er3+ ions. The photoluminescence measured under excitation of 808 nm laser diode (LD) displayed an ultra-broadband mid-infrared band emission with full width at half maximum (FWHM) of ~358 nm in tellurite glass with appropriate amount of Dy3+-Er3+ combination. This broadband mid-infrared band emission located in the range of 2550–3200 nm and originated from the spectral overlapping of 2.85 μm band emission of Dy3+:6H 13/2 → 6H 15/2 transition and 2.7 μm band one of Er3+:4I 11/2 → 4I 13/2 transition. Furthermore, the time resolved fluorescence decay behavior demonstrated the existence of energy transfer between Dy3+ and Er3+ ions which is responsible for the broadband luminescence, and the energy transfer efficiency was estimated. The present results indicate that tellurite glass co-doped with Dy3+-Er3+ ions is promising for applications in mid-infrared band luminescent sources and tunable lasers. • Dy3+/Er3+ co-doped tellurite glass was prepared by melt-quenching method. • An ultra-broadband 2550–3200 nm fluorescence emission with FWHM 358 nm was obtained. • Structural, thermal, spectroscopic properties and luminescent mechanism were investigated. • Dy3+/Er3+ co-doped tellurite glass is promising for MIR broadband tunable lasers. [ABSTRACT FROM AUTHOR]

• The structure and mid-infrared luminescence in glass ceramics was investigated. • Oxyfluoride germanosilicate glass ceramics with varied Si/Ge ratio are prepared. • The influence of Si/Ge ratio on mid-infrared luminescence of samples were discussed. • Prepared glass ceramics possesses high emission cross section and gain coefficient. Changes in glass structure and crystallization behaviour from oxyfluoride silicate glass to oxyfluoride germanate glass were studied by modifying the ratio of Si/Ge in oxyfluoride germanosilicate glass ceramics, and transparent glass ceramic with low light scattering and efficient mid-infrared emissions were obtained. The NaYF 4 nanocrystals crystallization ability of oxyfluoride glass was decreased with the increase in Ge content, which can be attributed to the weakened oxide and fluoride phase separation in GeO 2 -rich glass. Upconversion and down-conversion emission spectra together with Ho3+: 5I 6 energy level fluorescent decay curves have been discussed for SiO 2 -rich glass ceramics and GeO 2 -rich glass ceramics, in which the fluoride crystallization induced the decrease of multi-phonon non-radiative decay rates plays the main role in the energy transfer processes. The influence of Si/Ge ratio on 2 μm and 3 μm fluorescent emissions in glasses and glass ceramics, and its link with glass network structural changes were discussed. The optimized Yb/Ho codoped oxyfluoride germanosilicate glass ceramic with low light scattering, high peak emission cross section(11.18 × 10−21cm2) and maximum gain coefficient (1.387 cm−1) at 2888 nm provides a potential application in the development of new 3 μm laser devices based on transparent oxyfluoride glass ceramic materials. [ABSTRACT FROM AUTHOR]

• Er3+/Ho3+ co-doped tellurite glass was prepared by melt-quenching method. • Co-doping with Ho3+ enhanced the 2.7 µm band intensity of Er3+ by 39%. • ET micro-mechanism for this emission enhancement was quantitatively analyzed. • Er3+/Ho3+ doped tellurite glass with good thermal stability is promising for fiber lasers. Improving the mid-infrared band luminescent intensity in oxide glass system is a serious challenge. In this work, Ho3+ ions was introduced into Er3+ doped tellurite glass, and the improved effect on 2.7 µm band fluorescence of Er3+ was investigated. It was found that when 0.5 mol% of Ho 2 O 3 was incorporated into the tellurite glass with 0.5 mol% of Er 2 O 3 , the 2.7 µm band fluorescence intensity originating from Er3+:4I 11/2 → 4I 13/2 transition increased by about 39% under the excitation of 808 nm laser diode (LD). This significant enhancement was attributed to the energy transfers between Er3+ and Ho3+ ions which improved the population inversion ratio of this emission transition. Analyses of the intensity variations of visible and infrared band emissions as well as the fluorescence decay behavior of Er3+ ions with Ho3+ doped concentration demonstrated the existence of energy transfers, and the energy transfer mechanism was investigated by calculating the relevant micro-parameters to better clarify the origin of fluorescence enhancement. Additionally, Judd-Ofelt theory was applied to the absorption spectrum and the potential spectroscopic properties of Er3+ were evaluated, while DSC curves revealed the good thermal stability of the studied tellurite glass. All these indicated that Er3+/Ho3+ co-doped tellurite glass with appropriate concentrations is a promising candidate applied for 2.7 µm band optoelectronic devices. [ABSTRACT FROM AUTHOR]

Transparent Er3+/Yb3+ co-doped zirconium fluoride-chloride (ZFC) glass are firstly prepared for mid-infrared emission. The stronger 2750 nm emission from Er3+: ZFC glass is owing to a stronger covalence and local asymmetry of the crystal field around the Er3+ ions. The low phonon energy (600 cm−1) of ZFC glass are calculated from FTIR spectra and confirmed by Raman spectra. The low OH− concentration (9.75 × 10−17 cm−3) and high transmittance (1300-4000 cm−1) of ZFC glass are beneficial to mid-infrared emission. Co-doping rare earth ions Yb3+ enhances the 2750 nm emission. The energy transfer process between Yb3+ and Er3+ are identified based on luminescence spectra and decay curves. The role of Yb3+ plays the sensitizer on Er3+: 4I 11/2 and enhances the excited state absorption of Er3+: 4I 13/2 → 4F 9/2 , which is good for transition Er3+: 4I 11/2 → 4F 13/2. Thus, Er3+/Yb3+: ZFC glass with large emission cross section (1.06 × 10−20 cm2) is a potential laser application material. • The Er3+/Yb3+ co-doped zirconium fluoride-chloride glass is firstly prepared for 2.7 μm emission. • The transparent glass possess low OH– content (9.75 × 1017 cm–3). • The lifetime of Er3+: 4I 11/2 is as long as 3.05 ms. • The emission cross section around 2.7 μm emission is up to 1.06×10–20 cm2. [ABSTRACT FROM AUTHOR]

Ho3+/Yb3+ co-doped tellurite-germanate glasses with lower phonon energy (779 cm−1) and higher thermal stability were prepared by conventional melt quenching. The mid-infrared fluorescence spectra of the prepared glasses were investigated by 980 nm laser pumping. The full width at half maximum (FWHM) and lifetime of the sample at 2.0 μm were 186 nm and 8.09 ms, respectively. Compared with the reported glasses for this type, these values were effectively improved. In particular, the FWHM and emission lifetime of the prepared glass at 4.1 μm reached 276 nm and 8.17 ms, respectively, which have not been reported yet. Meanwhile, compared to the recently reported tellurite glasses, the ΔT was increased by approximate 22.7%. Strong up-conversion visible emission peaks at 547, 662, and 756 nm and near-infrared emission at 1.20 μm were observed in Ho3+/Yb3+ co-doped glass. Meanwhile, photoluminescence measurements showed that the doping of the appropriate amount of Yb3+ ions significantly enhanced the emission intensity of the samples at 2.0 μm and 4.1 μm. Therefore, the Ho3+/Yb3+ co-doped tellurite-germanate glass is a promising candidate for mid-infrared fiber and laser materials applications. • Ho3+/Yb3+ co-doped tellurite-tellurite glass has a lower phonon energy (779 cm−1). • Ho3+/Yb3+ co-doped tellurite-tellurite glass has a larger ΔT (200 °C). • The full width at half maximum (FWHM) of the sample at 4.1 μm reached 276 nm. • The emission lifetime of the prepared glass at 4.1 μm reached 8.17 ms • The FWHM and lifetime of the sample at 2.0 μm were 186 nm and 8.09 ms, respectively. [ABSTRACT FROM AUTHOR]

The ~3 μm fluorescence was investigated in the Ho 2 O 3 -doped transparent tellurite glass-ceramic for the first time. The branching-ratios and emission cross-sections were calculated. The glass-ceramics had high branching-ratio (20.5%) and large emission cross-section (1.76 × 10−20 cm2) corresponding to Ho3+:5I 6 →5I 7 transition. After crystallization, the ~3 μm fluorescence intensity increased obviously excited by 640 nm laser diode. The broadband fluorescence about 3 μm was observed under excitation by a 1950-nm thulium-doped fiber lasers. The increased ~3 μm fluorescence intensity and narrowed spectrum demonstrated the Ho3+ ions embedded into the crystalline phase. These results indicate that the tellurite glass-ceramics may be a promising material for mid-infrared lasers. • ~3 μm emission of Ho3+ doped tellurite GC was studied for the first time. • The emission cross section for 3 μm emission in GCH reached to 1.76 × 10−20 cm2. • Excited by 1950 nm thulium-doped fiber lasers, the 3 μm emisson were observed. • The emission intensity of GCH in the range of 2700–2760 nm increased nine times. • The ~3 μm emission spectrum in GCH narrowed obviously. [ABSTRACT FROM AUTHOR]