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ABSTRACT: An investigation of spectroscopic property and energy transfer process of Er3+ doped and Er3+/Yb3+ co-doped germanate glasses is presented. The emission cross section of the 4I11/2 → 4I13/2 transition of Er3+ doped germanate glass is calculated to be 1.2 × 10−20 cm2. The microparameter of energy transfer from Yb3+:2 F5/2 to Er3+:4I11/2 is calculated to be 2.74 × 10−39 cm6/s, and that is not phonon dependent in the quasiresonant process. The intensity of the emission around 2.7 μm is enhanced obviously when Er3+ co-doped with Yb3+. The excited-state relaxation process of Er3+ is adequately described by a combination of the Judd-Ofelt model and the energy-gap law. With the exception of 4I13/2 and 4I11/2 levels, multiphonon relaxation is dominant for all excited states, making it possible to efficiently pump the 1.55 μm 4I13/2 → 4I15/2 and 2.7 μm 4I13/2 → 4I11/2 emission by excitation of Yb3+:2F5/2 and Er3+:4I11/2 at 980 nm.
Journal of Applied Physics 02/2012; 111(3):033524-033524-7. · 2.17 Impact Factor
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ABSTRACT: The structural origin and laser performance of thulium-doped germanate glasses have been studied. The investigation includes two main sections. The first part discusses the Raman spectroscopic and thermal stability of the host glass structure. The low value of the largest phonon energy (850 cm(-1)) reduces the probability of nonradiative relaxation. The large emission cross section of the Tm(3+) : (3)F(4) level (8.69 × 10(-21) cm(2)), the high quantum efficiency of the (3)F(4) level (71%), and the low nonradiative relaxation rate of the (3)F(4) → (3)H(6) transition (0.09 ms(-1)) illustrate good optical properties of the germanate glass. In the second part, the room-temperature laser action from the thulium-doped germanate glass is demonstrated when pumped by a 790 nm laser diode. The maximum output power of 346 mW and slope efficiency of 25.6% are achieved.
The Journal of Physical Chemistry A 11/2011; 115(49):14163-7. · 2.95 Impact Factor
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ABSTRACT: This Letter reports intense emission at 2.7 μm and broadband emission at 2.0 μm from Er(3+)/Tm(3+)/Ho(3+)-doped fluorophosphate glass. The fluorescence characteristics and energy transfer upon excitation of a conventional 980 nm laser diode are investigated. Based on the fluorescence spectra and lifetime measurement, the effect of Tm(3+) and Ho(3+) ions on intense 2.7 μm emission in fluorophosphate glass is demonstrated. It is also found that the effective bandwidth of 2.0 μm emission due to Tm(3+) and Ho(3+) ions can reach as high as 196 nm. These results indicate that the advantageous spectroscopic characteristics of Er(3+)/Tm(3+)/Ho(3+) triply doped fluorophosphate glass together with the outstanding thermal properties may become an attractive host for the mid-IR solid state lasers.
Optics Letters 08/2011; 36(16):3218-20. · 3.40 Impact Factor
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ABSTRACT: To detect and analyze two important genes, comE and luxS, in quorum sensing signal pathway from Streptococcus oralis (S. oralis).
The total genomic DNA of S. oralis NH521 (a clinically isolated strain) was firstly extracted. The comE and luxS genes were then amplified by polymerase chain reaction (PCR) and further sequenced. The obtained sequences were compared with related sequences in GenBank.
Target bands of both comE and luxS genes were detected by electrophoresis. The obtained gene sequences were similar to the corresponding sequences from another S. oralis strain (luxS, 95.0%; comE, 99.6%); however, comparing to gene sequences of another species Streptococcus mutans, comE was more divergent (12.7%) than luxS gene (74.1%).
This study successfully amplified and sequenced comE and luxS genes from S. oralis NH521 strain. The luxS gene accumulated more mutations than comE gene did between two S. oralis strains, but comE gene is more divergent than luxS gene between two Streptococcus species.
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 08/2011; 29(4):355-7.
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ABSTRACT: 2.7 μm emission properties and energy transfer mechanism of Nd<sup>3+</sup>/Er<sup>3+</sup> co-doped sodium tellurite glasses are investigated in present paper. Absorption and emission spectra were tested to characterize the 2.7 μm emission properties of Nd<sup>3+</sup>/Er<sup>3+</sup> co-doped sodium tellurite glasses and a reasonable energy transfer mechanism of 2.7 μm emission between Er<sup>3+</sup> and Nd<sup>3+</sup> ions was proposed. Intense 2.7 μm emission was obtained from Nd<sup>3+</sup>/Er<sup>3+</sup> co-doped sodium tellurite glasses due to the efficient energy transfer from Nd<sup>3+</sup> to Er<sup>3+</sup> ions under 808 nm LD pumping. Meanwhile, strongly decreased 545 nm up-conversion and 1.5 μm emissions were observed. Additionally, to obtain efficient 2.7 μm emission, the optimized concentration ratio of Nd<sup>3+</sup> to Er<sup>3+</sup> was found to be 0.5:1 in present glass system. Our results suggest that the present Nd<sup>3+</sup>/Er<sup>3+</sup> co-doped sodium tellurite glass might have potential application in mid-infrared lasers.
Journal of Applied Physics 08/2011; · 2.17 Impact Factor
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ABSTRACT: The 2.7 μm emission has been obtained using 980 nm laser excitation in Er3+/Tm3+/Pr3+ triply doped ZrF4–BaF2–LaF3–AlF3–YF3 glass. 2.7 μm emission characteristics and energy transfer are investigated. Population inversion between the 4I11/2 and 4I13/2 levels is significantly enhanced by way of Tm3+ and Pr3+ co-doping into Er3+-doped fluoride glass. These results indicate that this Er3+/Tm3+/Pr3+ triply doped fluoride glass has potential applications in 2.7 μm laser.
Journal of the American Ceramic Society 07/2011; 94(8):2289 - 2291. · 2.27 Impact Factor
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ABSTRACT: Intense 2.0 μm emission has been obtained from Ho3+/Tm3+/Yb3+ triply doped fluorophosphate glass pumped by a conventional 980 nm laser diode. The spectroscopic properties and energy transfer mechanisms between Ho3+, Tm3+ and Yb3+ are analyzed. Based on the absorption spectra, the Judd-Ofelt parameters, radiation emission rates, radiative lifetime and branching ratios of Ho3+ ions are calculated. It is also found that the 2.0 μm emission of Ho3+ can be greatly enhanced under the excitation at 980 nm by incorporating Tm3+ and Yb3+ simultaneously. Additionally, the micro-parameters of the energy transfer processes are quantitatively analyzed. The energy transfer coefficient from Yb3+ to acceptors and from Tm3+ to Ho3+ can reach as high as 13.14 × 10−40 cm6/s and 23.39 × 10−40 cm6/s, respectively. This Ho3+/Tm3+/Yb3+ doped fluorophosphate glass possessing high energy transfer coefficient and excellent thermal stability is a promising candidate for efficient 2.0 μm laser.
Journal of Applied Physics 07/2011; 110(3):033502-033502-6. · 2.17 Impact Factor
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ABSTRACT: A detailed characterization of structural analysis and energy transfer (ET) process in Tm(3+) doped germanate glasses has been presented. The thermal stability and Raman spectroscopic analysis of the host glass structure has been discussed. It is observed that replacing GeO(2) by Ga(2)O(3) resulted in decreasing of glass transition temperature and largest phonon energy. Increasing concentration of Ga(2)O(3) decreases the density of cross-linking of the germanate glass network, and weaker Ga-O bonds result in lower phonon energy. The influences of the concentrations of Ga(2)O(3) and the glass structure on the ET have also been analyzed. The extended overlap integral method is used to calculate the microparameters of the energy transfer and the critical distance. The results show that the transference Tm → Tm ((3)H(4), (3)H(6) → (3)H(6), (3)H(4)) energy migration is not phonon dependent in the quasiresonant processes, while the cross relaxation Tm → Tm ((3)H(4), (3)H(6) → (3)F(4), (3)F(4)) is a multiphonon mechanism dominated by one-phonon creation (∼96%). It is demonstrated that the stretching frequencies and the ET processes become lower when increasing the concentration of Ga(2)O(3).
The Journal of Physical Chemistry A 06/2011; 115(24):6488-92. · 2.95 Impact Factor
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ABSTRACT: Effect of Ce3+ ions introduction on 2 μm emission properties and energy transfer mechanism in Yb3+/Ho3+-doped fluorophosphate glass has been investigated. From the measured fluorescence spectra, strong emission near 2 μm is demonstrated due to the sensitization of Yb3+ and Ce3+. Based on the absorption spectra, the Judd-Ofelt parameters and radiative properties were calculated and compared with those of other glass hosts. In addition, the energy transfer coefficient from Yb3+ to Ho3+ is 9.52 × 10−40 cm6/s in Yb3+/Ho3+/Ce3+ triply doped sample and is three times larger than that in undoped Ce3+ sample. These results suggest that this Yb3+/Ho3+/Ce3+ fluorophosphate glass with excellent thermal stability and efficient energy transfer from Yb3+ to Ho3+ is a good candidate for 2 μm laser.
Journal of Applied Physics 04/2011; 109(8):083535-083535-6. · 2.17 Impact Factor
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ABSTRACT: A novel Er(3+)/Pr(3+) codoped germanate glass was fabricated and analyzed. Efficient emission at 2.7 μm from the glass was observed upon excitation of a conventional 980 nm laser diode. The 2.7 μm emission characteristics and energy transfer (ET) were investigated. Population inversions between ⁴I(13/2) and ⁴I(11/2) levels have been achieved, and an enhanced emission from 2550 to 2800 nm was obtained. Large ET efficiency of 95% indicates that the ET process from Er(3+) to Pr(3+) (⁴I(13/2), ³H₄)→(⁴I(15/2), ³F₃) is efficient and that Pr(3+) can enhance the emission of 2.7 μm by quenching the lower laser level of Er(3+) via ET.
Optics Letters 04/2011; 36(7):1173-5. · 3.40 Impact Factor
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ABSTRACT: This work reports the intense emission at 2.7 μm in a Er(3+)/Pr(3+)-codoped fluorophosphate (FP) host glass. This FP glass shows good thermal stability and high transmittance around 3 μm. The emission characteristic and energy transfer upon excitation of a conventional 980 nm laser diode are investigated. The prepared glass possesses higher spontaneous transition probability (22.16s(-1)) along with a larger calculated emission cross section (6.57 ± 0.11) × 10(-21) cm(2) corresponding to the laser transition (4)I(11/2)→(4)I(13/2). In addition, the effect of Pr(3+) codoping on the 2.7 μm photoluminescence in FP glass is demonstrated. Hence, the advantageous spectroscopic characteristics of Er(3+)/Pr(3+)-codoped FP glass together with the outstanding thermal property indicate that this kind of glass may become an attractive host for developing solid-state lasers at around 2.7 μm.
Optics Letters 01/2011; 36(2):109-11. · 3.40 Impact Factor
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ABSTRACT: A new type of fluorophosphate glasses with high thulium doping concentration (up to 10 mol % Tm <sup>3+</sup> ) is investigated. The intensive 1.8 μ m fluorescence is demonstrated with lower concentration quenching. On the basis of the measured Raman spectroscopy, it is revealed that the glass structure will be changed when adding Tm <sup>3+</sup> ions into fluorophosphate glasses. Besides, the Judd–Ofelt parameters and radiative properties are calculated and discussed based on Judd–Ofelt theory. And the absorption and emission cross-sections of <sup>3</sup> F <sub>4</sub>→<sup>3</sup> H <sub>6</sub> transition are also calculated by using McCumber and Beer–Lambert theories.
Journal of Applied Physics 11/2010; · 2.17 Impact Factor
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ABSTRACT: Ho <sup>3+</sup> doped germanate glass sensitized by Yb <sup>3+</sup> has been investigated for potential application as a near-infrared laser material. The characteristic temperatures are determined by differential scanning calorimeter, and the absorption and emission spectra are measured. According to absorption spectra, Judd–Ofelt parameters and radiative transition probabilities are calculated and analyzed by Judd–Ofelt theory. The intensity of emission spectra shows a strong dependence upon the Yb <sup>3+</sup> concentration. The result also indicates that Yb <sup>3+</sup> plays an important role in the emission of 2.0 μ m by transferring the 980 nm excitation energy to Ho <sup>3+</sup> . The energy transfer process from Yb <sup>3+</sup> to Ho <sup>3+</sup> is analyzed and the result shows that coefficient of the forward energy transfer Yb <sup>3+</sup>→ Ho <sup>3+</sup> is 19 times of magnitude larger than that of the backward energy transfer Yb <sup>3+</sup>← Ho <sup>3+</sup> . It is found that the highest gain in 2.0 μ m region could be achieved from the germanate glass with 5.0 mol % Yb <sub>2</sub> O <sub>3</sub> and 1.0 mol % Ho <sub>2</sub> O <sub>3</sub> . The present Yb <sup>3+</sup>/ Ho <sup>3+</sup> codoped germanate glass with high emission cross section of Ho <sup>3+</sup>:<sup>5</sup> I <sub>7</sub>→<sup>5</sup><r-
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oman>I <sub>8</sub> at 2.0 μ m and efficient energy transfer from Yb <sup>3+</sup> to Ho <sup>3+</sup> will be a suitable material for developing solid state lasers around 2.0 μ m .
Journal of Applied Physics 09/2010; · 2.17 Impact Factor
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ABSTRACT: Broadband near-infrared emission has been investigated in a new type host composition of Er3+–Tm3+ codoped germanate glass. A broadband emission extend from 1350 to 1675 nm with the full width at half maximum (FWHM) around 138 nm is obtained in the germanate glass which codoped with 0.2 wt.% Er2O3 and 0.8 wt.% Tm2O3. The energy transfer between Er3+ and Tm3+ plays an important role in the emission mechanism, which is evidenced by the visible upconversion and the lifetime of Er3+:4I13/2 level effected by the addition of Tm2O3. And energy transfer efficiency from Er3+ to Tm3+ reaches 76% for the highest Tm3+ concentration of 0.8 wt.%. These results suggest that this glass would be a promising material for broadband light source and broadband amplifier for the wavelength division multiplexing transmission systems.
Optical Materials. 33(3):299-302.
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ABSTRACT: Transparent oxyfluoride glass and glass ceramics doped with 3.0 mol% Yb3+ and 0.5 mol% Ho3+ ions have been prepared. The investigated samples show efficient 2.0 μm emission. The absorption and emission cross sections corresponding to the 5I7–5I8 transitions of Ho3+ (at 2.0 μm) have been calculated according to the McCumber theory. Glass sample heat-treated at 470 °C has the maximum absorption and emission cross sections of 5.58 × 10−21 cm2 at 1949 nm and 6.64 × 10−21 cm2 at 2034 nm. The Yb3+–Ho3+ doped oxyfluoride glass ceramic exhibits an advantage for application in 2.0 μm laser devices.
Optical Materials. 32(11):1451-1455.
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ABSTRACT: TmF3 doped TeO2–ZnO–La2O3 (TZL) glasses and fibers have been prepared by the conventional melt-quenching and suction casting methods, respectively. 2 μm emission properties and energy transfer mechanisms of the TZL glasses and fibers have been analyzed and discussed. The oscillator strength, Judd–Ofelt parameters, radiative transition probability and radiative lifetime of Tm3+ have been calculated based on the absorption spectra and Judd–Ofelt theory. The maximum emission cross-section of Tm3+ is 6.9 × 10−21 cm2 near 2 μm. Emission spectra have been obtained from both TZL fibers and bulk glass when excited with a 794 nm pump. The results of 2 μm emission spectra indicate that the line width of Tm3+ measured in fibers is narrower than that in the bulk glass sample. The peak position of the emission spectra shifts to longer wavelength with increment of the fiber length.
Journal of Non-Crystalline Solids 357:2489-2493. · 1.54 Impact Factor
