Ruoshan Lei

Synthesis, theoretical analysis, and characterization of highly Er 3+ doped fluoroaluminate–tellurite glass with 2.7 μm emission

The synthesis, theoretical analysis, and optical characterizations of fluoroaluminate–tellurite glasses with high Er3+ concentration are reported. The 2.7 μm emission from Er3+ doped fluoroaluminate–tellurite glasses upon excitation of a conventional 980 nm LD is demonstrated with minimized concentration quenching. The prepared glass possesses high fluorescence lifetime of 4I11/2 level (1.343ms) and large calculated emission cross section (7.63 × 10−21 cm2). Besides, the radiative transfer microscopic parameters of 4I11/2 and 4I13/2 levels were theoretically analyzed. Hence, these results indicate that this Er3+ doped fluoroaluminate–tellurite glass has potential applications in 2.7 μm laser.

Positive influence of Ce 3+ on effective transfer Yb 3+ : 2 F 5/2 → Ho 3+ : 5 I 6 in silica-germanate glass for mid-infrared applications

A1.5 time enhancement of a 2.0 μm emission was achieved successfully in Yb3+/Ho3+ doped silica-germanate glass with a 0.1 mol% Ce3+ addition, which possesses a larger emission cross section (4.43 × 10−21 cm2). According to the measured absorption spectra, the Judd-Ofelt parameters and radiative properties were calculated and discussed. The energy transfer mechanisms existed in Ho3+, Yb3+ and Ce3+ ions were investigated based on absorption, upconversion and fluorescence spectra. Meanwhile, the decay profiles of several levels were measured to further examine the enhanced mid-infrared emissions. Moreover, a high energy transfer microscopic parameter (7.54 × 10−40cm6/s) of Yb3+→Ho3+ process was obtained when 0.1 mol% Ce3+ ions were introduced into the Ho3+/Yb3+ system. All results indicate that the Yb3+/Ho3+/Ce3+ tri-doped silica-germanate glass is a promising candidate material for improving the Ho3+ 2.0 μm fiber laser performance.

Influence of excitation power and doping concentration on the upconversion emission and optical temperature sensing behavior of Er 3+ : BaGd 2 (MoO 4 ) 4 phosphors

Generally, the effects of excitation power and dopant concentration on the optical temperature sensing behaviors of rare earth (RE) doped materials based on the fluorescence intensity ratio (FIR) technique are disregarded. In this paper, Er3+: BaGd2(MoO4)4 phosphors with different concentrations were fabricated by the high temperature solid-state reaction method. The results show that the variation of FIR (2H11/2/4S3/2) with excitation power is not only related to the laser-induced heating effect, but also the diverse power-dependences of 2H11/2 and 4S3/2 levels. Consequently, the temperature calibration curves change at different excitation power densities. When the calibration curve obtained at a low power density is applied to estimate the temperature of the object excited at a high power density, a large overestimate of the temperature rise induced by the optical heating effect can be caused. Besides, the temperature sensing sensitivity depends on the Er3+ doping concentration, which increases first with concentration to a maximum and then reduces. The maximal absolute sensitivity is ~110.5 × 10−4 K−1 in 5mol% Er3+: BaGd2(MoO4)4 phosphor, which is among the highest values of RE ions doped phosphors based on thermally coupled levels recorded before.

A portable all-fiber thermometer based on the fluorescence intensity ratio (FIR) technique in rare earth doped TeO2–WO3–La2O3–Na2O glass

A portable all-fiber thermometer based on the FIR technique in Er3+/Yb3+ co-doped TeO2–WO3–La2O3–Na2O (TWLN) glasses was designed and its temperature sensing performance in the temperature range of 293–569 K was determined in detail. The high glass transition temperature (Tg = 439 °C) of TWLN glass contributes to broadening the range of temperature measurement. The spectroscopic analysis of Eu3+ ions and Judd–Ofelt analysis of Er3+ ions reveal that the rare earth ions are situated in a low symmetry environment in TWLN glass, which suggests that a large FIR change and high temperature sensitivity are expected. Intense green upconversion emission in Er3+/Yb3+ co-doped TWLN glass fiber was easily observed under 980 nm excitation at a low pumping power (1.4 mW). The maximum temperature sensitivity of the portable all-fiber thermometer reached 86.7 × 10−4 K−1 at 553 K. Experimental results showed that the absolute errors were around ±1 K within the temperature range from 285 to 563 K.

Low temperature formation of AlN nanofibers by carbothermal reduction nitridation of hydrothermal precursor fibers

Abstract AlN nanofibers were fabricated by carbothermal reduction (CRN) method of hydrothermal precursor fibers using aluminum nitrate, urea, glucose and polyethylene glycol as raw materials. The as-fabricated samples were characterized by TG-DSC, XRD, SEM, EDS, and UV–vis absorption and PL spectra. The results indicated that raw materials were transformed to NH4Al[(OOH)HCO3] (AACH) fibers in hydrothermal process, carbon coated γ-Al2O3 fibers in decomposition process, and AlN nanofibers in CRN process. In relation to other CRN methods, the hydrothermal precursors reduced the fabrication temperature in 200 °C. The diameter of the AlN nanofibers fabricated at 1400 °C was 90–110 nm with several micrometers length. These fibers showed broad absorption band from 190 to 230 nm with an absorption edge at 198 nm and obvious emission at approximately 478 nm and 577 nm excited by 350 nm, indicating a valuable application in light-emitting nanodevices. Such a strategy can be extended to synthesize other nitride fibers.

Emission properties of 1.8 and 2.3 μm in Tm3+-doped fluoride glass

In this work a Tm3+-doped fluoride glass with good thermal stability is prepared. Intensive 1.8 and 2.3 μm emissions are obtained when pumped by an 800 nm laser diode. And the 1.48 μm emission is limited because of the much strong radiation around 1.8 μm. On the basis of absorption spectrum, radiative properties are investigated and discussed according to Judd–Ofelt parameters (Ω2, Ω4, Ω6) calculated by Judd–Ofelt theory. Besides, absorption and emission cross-sections of 3F4 → 3H6 transition are figured out and analyzed by using McCumber and Beer–Lambert theories. The high gain around 1.8 μm was predicted by the large σemiτrad product (29.8 × 10–21 cm2 ms). The results obtained indicate that the Tm3+-doped fluoride glass can be a promising 2.0 μm laser glass material.