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ABSTRACT: The spectra of Er<sup>3+</sup>:CaGdAlO<sub>4</sub> and Pr<sup>3+</sup>/Er<sup>3+</sup>:CaGdAlO<sub>4</sub> crystals were measured under the same conditions. With the presence of Pr<sup>3+</sup> ions, the intensities of the green, red upconversion and near-infrared emissions are dramatically reduced to 1/20, 1/150, and 1/8.5 of those for Er<sup>3+</sup>:CaGdAlO<sub>4</sub>. Furthermore, the lifetimes of I<sub>11/2</sub>4 upper and I<sub>13/2</sub>4 lower laser levels fall from 450 and 982 μs to 84.8 and 74.3 μs. It is obvious that the self-saturation for Er<sup>3+</sup> 2.7 μm laser is effectively suppressed. The energy transfer efficiencies and coefficients of Er<sup>3+</sup>→Pr<sup>3+</sup> are also calculated. These results indicate that Pr<sup>3+</sup> codoping is beneficial in achieving 2.7 μm laser in Pr<sup>3+</sup>/Er<sup>3+</sup>:CaGdAlO<sub>4</sub> crystal.
Optics Letters 12/2012; 37(23):4838-40. · 3.40 Impact Factor
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01/2012; , ISBN: 978-953-307-610-2
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ABSTRACT: Rare-earth ions doped Gd3Ga5O12 nanocrystals have been prepared by a propellant combustion synthesis method and their up-conversion properties were systematically investigated in this paper. XRD, SEM, TEM, and up-conversion emission spectra were used to characterize the synthesized nanocrystals. Energy transfer from Yb3+ to Er3+ and Tm3+ can occur simultaneously in the as-synthesized Gd3Ga5O12 nanocrystals. The up-conversion mechanisms and relevant energy transfer processes are discussed. A white light generation was observed when the Yb3+, Er3+ and Tm3+ were directly incorporated in the Gd3Ga5O12 lattice. And its calculated color coordinates is (0.35, 0.41) under the excitation at 974.5 nm. The bright white luminescent nanocrystals may have potential application in the field of lighting, displays and photonics.
Journal of Nanoscience and Nanotechnology 10/2010; 10(10):6527-33. · 1.56 Impact Factor
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ABSTRACT: High optical quality Dy3+-doped Gd3Ga5O12 (abbreviated as Dy : GGG below) crystal was grown by the Czochralski technique along the (1 1 1) orientation. The absorption spectrum, fluorescence spectrum and fluorescence decay curve of Dy : GGG have been recorded at room temperature. Based on the Judd–Ofelt (J–O) theory, the intensity parameters from the measured line strengths were determined. The J–O parameters were used to predict radiative transition probabilities, radiative lifetime and branching ratios for various excited levels of the Dy : GGG crystal. In the visible region, one intense fluorescence band was observed at 581 nm, corresponding to the 4F9/2 → 6H13/2 transition. The room-temperature fluorescence lifetime of this transition of Dy3+ ion in the GGG crystal was measured to be 0.79 ms, and the luminescent quantum efficiency of the 4F9/2 level was evaluated to be 71.4 %. The emission cross-sections of the 4F9/2 → 6H13/2 transition were estimated by the use of the Füchtbauer–Ladengurg method. The research on the emission at 581 nm indicates the possibility of using a commercially available laser diode of 353 nm as a pumping source for a solid-state yellow laser.
Journal of Physics D Applied Physics 02/2010; 43(7):075402. · 2.54 Impact Factor
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ABSTRACT: Heavily Er3+-doped and Er3+/Pr3+ co-doped Gd3Ga5O12 (abbreviated as Er : GGG and Er,Pr : GGG, respectively) laser crystals were synthesized by the Czochralski method. The synthesized laser crystals were characterized by absorption, up-conversion fluorescence, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence, and luminescence decay measurements. The optical parameters related to absorption and emission cross-sections and fluorescence lifetimes were evaluated and compared. It was found that the up-conversion and NIR fluorescence weaken, at the same time Mid-IR fluorescence intensity strengthens with the increment of Er dopant concentration or co-doping with Pr3+ in Er : GGG crystals. Furthermore, the self-termination bottleneck was broken successfully in the Er,Pr : GGG crystal, and the energy transfer efficiencies of Er3+ : 4I11/2 → Pr3+ : 1G4 and Er3+ : 4I13/2 → Pr3+ : 3F4 were determined.
Journal of Physics D Applied Physics 10/2009; 42(21):215406. · 2.54 Impact Factor
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ABSTRACT: Neat and Dy3+-doped Gd3Ga5O12 nanocrystals have been successfully prepared via a propellant combustion method. A broad-band photoluminescence (PL) blue emission at 430 nm related to Ga2O3 in the Gd3Ga5O12 nanocrystals is observed. The characteristic PL emissions of Dy3+ and the broad-band PL blue emission at 430 nm can be observed in Gd3Ga5O12/Dy3+ samples. An energy transfer process from the host “luminescent centers” to Dy3+ is demonstrated. The lifetimes of the broad-band PL blue emission and the characteristic PL emission of Dy3+ are estimated. The efficiency of this energy transfer is determined up to 19.6%. The study on the influence of the excitation wavelength and the doping concentration of Dy3+ on the luminescent emission of the samples was performed under the excitation of different UV wavelengths. A white light with the CIE (Commission International de l′Eclairage) color coordinates (0.32, 0.34) was achieved. This material may find potential applications in lighting, optoelectronics, and imaging technologies.
02/2009;
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ABSTRACT: Room-temperature bright white up-conversion (UC) luminescence in Yb3+/Er3+/Tm3+ ion-doped YAlO3 nanocrystals was achieved under diode laser excitation of 974.5 nm. The white light consists of the blue (1G4 → 3H6 of Tm3+), green (2H11/2/ 4S3/2 → 4I15/2 of Er3+), and red (1G4 → 3F4 of Tm3+ and 4F9/2 → 4I15/2 of Er3+) UC emissions. The UC mechanisms were proposed based on spectral, pump power dependence and kinetic analyses. The white light may be a possible candidate for applications in the field of lighting, displays, and photonics.
08/2008;
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ABSTRACT: We report in the present paper the Yb <sup>3+</sup> -doped Y <sub>2</sub> Ca <sub>3</sub> B <sub>4</sub> O <sub>12</sub> diode-pumped laser operation in both continuous-wave (cw) and passively Q -switched modes. The differential slopes of the cw output power are in the 22%–40% range under different experimental conditions. Continuous tuning of the laser wavelength is obtained in the 1020–1057 nm range, in agreement with the broad emission spectra. In pulsed regime the repetition rate occurs up to 1.6 kHz and pulse energies of 30–75 μ J with about 40 ns duration are obtained.
Journal of Applied Physics 08/2008; · 2.17 Impact Factor
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ABSTRACT: The polarized absorption spectra, polarized fluorescence spectra and fluorescence decay curve of Pr3+-doped NaLa(WO4)2 single crystals were measured at room temperature. The emission cross section has been presented and Judd–Ofelt theory has been applied to the analysis of the absorption spectra. The calculated radiative lifetime is compared with the experimental data for the 3P0 emitting level. The result indicates that the relaxation of the excited 3P0 level of praseodymium is governed by radiative transitions, which makes the 3P0 manifold of the Pr3+-doped NaLa(WO4)2 crystal promising as the upper laser level.
Journal of Physics D Applied Physics 07/2008; 41(16):165404. · 2.54 Impact Factor
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ABSTRACT: The vacuum ultraviolet excitation and ultraviolet-visible emission spectra are reported for the laser and upconverter material KPb2Cl5:Er3+. The low-phonon energies of the host lattice enable, in addition to the ten luminescent states of Er3+ in the visible and infrared spectral regions at room temperature, the observation of a further two luminescent multiplet terms in the ultraviolet spectral region at 10 K. A careful distinction is made between 4f11–4f11 Er3+ transitions and the band to band and Pb2+ transitions.
Applied Physics Letters 03/2008; 92(10):101115-101115-3. · 3.84 Impact Factor
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ABSTRACT: Crystals of NaLa(WO4)2 : Ho3+ were grown by the Czochralski method. The spectroscopic properties have been investigated at room temperature. Intensity parameters, radiative lifetimes and branching ratios have been calculated in the framework of Judd–Ofelt theory. The luminescence spectra measured under 450 nm pumping are dominated by a strong green emission in the 550 nm region connected with the 5S2 + 5F4 → 5I8 transition. The stimulated emission cross-section for this transition was estimated. The luminescence decay curve of the 5S2 + 5F4 level was also measured at room temperature.
Journal of Physics D Applied Physics 09/2007; 40(19):5883. · 2.54 Impact Factor
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ABSTRACT: This paper reports crystal growth and optical characteristics of dysprosium (Dy3+) and erbium (Er3+) doped mid-infrared laser crystal ternary-potassium-lead-chloride (KPb2Cl5). Two transparent crystals with good optical quality have been grown successfully by using the Bridgman technique,the largest crystal size reaches up to ∅10×60mm2. Measurements of X-ray diffraction(XRD) and absorption spectra were carried out. Based on Judd-Ofelt theory, the intensity parameters Ωt(t=2,4,6), the experimental and theoretical oscillator strengths have been obtained.The intensity parameters Ωt(t=2,4,6) of Er3+:KPb2Cl5 were calculated to be Ω2=5.10×10-20 cm2, Ω4=1.25×10-20 cm2, Ω6=0.83×10-20 cm2, and the values for Dy3+:KPb2Cl5 were calculated to be Ω2=6.26×10-20 cm2, Ω4=2.45×10-20 cm2, Ω6=0.04×10-20 cm2 respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal Research and Technology 08/2007; 42(11):1063 - 1067. · 0.95 Impact Factor
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ABSTRACT: Ho3+-doped SrWO4 crystal was grown by the Czochralski method. The polarized absorption and emission spectra together with the fluorescent decay curve were measured at room temperature. The intensity parameters, radiative lifetimes and branching ratios were calculated based on the Judd–Ofelt theory. The stimulated emission cross-sections of the potential laser transitions were determined using the reciprocity method.
Journal of Physics D Applied Physics 03/2007; 40(7):1902. · 2.54 Impact Factor
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ABSTRACT: The authors report the passive Q switching of a diode pumped Yb:GdAl3(BO3)4 (Yb:GAB) laser. The slopes of the average output power are 25% and 39.5% under different experimental conditions. The repetition rates occur in the 1–4.5 kHz range and pulse energies of 125 and 165 μJ with about 30 ns duration are obtained. An experimental comparison with passively Q-switched Nd:GAB laser is provided. A theoretical analysis is performed. It is in reasonable agreement with the experimental data and it is shown to be a useful tool for predicting the optimization of the cavity parameters.
Applied Physics Letters 02/2007; 90(7):071103-071103-3. · 3.84 Impact Factor
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ABSTRACT: From two positions of the concave output mirror of the laser cavity, diode-pumped ordinary or extraordinary polarization lasing
of an Yb3+-doped GdAl3(BO3)4 nonlinear birefringent crystal is obtained. Translating the mirror at an intermediate position, simultaneous ordinary and
extraordinary polarization lasing at 1046 (2.5nm FWHM) and 1040nm (2.2nm FWHM), respectively, is obtained with up to 53%
slope efficiency. Using a YAG:Cr4+ saturable absorber for passive Q-switching the cavity, ordinary and extraordinary pulses are obtained with an energy as high
as 236μJ and with about 30ns duration. The two pulses of orthogonal polarizations can be separated by up to a few hundred
ns, depending on the experimental conditions. The simultaneity of the pulses is observed but is difficult to maintain. A model
constituted by two coupled equations reproduces reasonably well the experimental data. Repetition rates up to 3kHz have been
explored, corresponding to 4.65W absorbed pump power.
Applied Physics B 01/2007; 89(2):323-328. · 2.19 Impact Factor
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ABSTRACT: A Pr <sup>3+</sup> -doped Na Gd ( W O <sub>4</sub>)<sub>2</sub> single crystal has been grown by the Czochralski technique along the (0 0 1) orientation. The refractive indices were measured precisely as a function of wavelength. A Raman spectrum, polarized absorption spectra, fluorescence spectra, and fluorescence decay curve have been recorded at room temperature. The standard and modified Judd-Ofelt theories have been performed to analyze the absorption spectra to determine the spectroscopic parameters, including the Judd-Ofelt intensity parameters Ω<sub>t</sub> (t=2,4,6) , radiative transition probabilities, radiative lifetimes, and branching ratios. The stimulated emission cross sections and fluorescence lifetime of the promising laser level were obtained.
Journal of Applied Physics 01/2007; · 2.17 Impact Factor
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ABSTRACT: TmAl3(BO3)4 crystallizes in the trigonal system R32 (No. 155) with a = b = 9.2741(13) A, c = 7.218(3) A, alpha = beta = 90 degrees , gamma = 120 degrees , V = 537.7(2) A(3), D(c) = 4.494 g cm(-3), and Z = 3. The absorption spectrum of this crystal was recorded at room temperature. The Judd-Ofelt (J-O) theory was applied to the absorption intensities of TmAl(3)(BO3)4 to obtain the three J-O parameters: Omega(2) = 2.40 x 10(-20) cm(2), Omega(4) = 0.48 x 10(-20) cm(2), and Omega(6) = 1.09 x 10(-20) cm(2). The radiative probabilities, radiative lifetimes, and branching ratios of TmAl3(BO3)4 were calculated. The absorption and emission cross sections, together with the potential laser gain near 1.9 microm, were investigated. The potential laser gain curves indicate that the tunability range is about 200 nm.
Inorganic Chemistry 12/2006; 45(23):9326-31. · 4.60 Impact Factor
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ABSTRACT: The crystal of ZnWO4 doped with Co2+ has been grown by the Czochralski technique. The orientation procedure was presented. Along the crystallographic axes, the principal coefficients of thermal expansion and absorption spectra were measured and discussed. Based on the data, the crystal field parameter 10Dq, Racah parameter B, as well as the absorption cross sections were calculated. The nonlinear dependence of optical absorption on concentration of cobalt ions was found and discussed in single crystal Co2+:ZnWO4. The results indicate that inner defects such as natural cleavage or slip faces in crystal are important in the study of optical and thermal properties.
Journal of Applied Physics. 11/2006; 100(10):103514-103514-5.
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ABSTRACT: A systematic investigation of room temperature absorption and emission spectra were presented for trivalent holmium in a crystal of NaY(MoO4)2. Oscillator strengths of the transitions to all levels up to 361 nm were calculated from the absorption spectra. Judd–Ofelt intensity parameters of Ho3+ were used to calculate the radiative transition rates, branching ratios and radiative lifetimes. The emission cross-sections for the 5S2 → 5I8 and 5I7 → 5I8 transitions of special interest for laser application were determined.
Journal of Physics D Applied Physics 08/2006; 39(17):3755. · 2.54 Impact Factor
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ABSTRACT: The polarized absorption, emission spectra, and the fluorescence decay curve of Er3+ ions in the anisotropic Ca3(BO3)2 crystal were investigated at room temperature. The experimental oscillator strengths for the transitions from the ground state to excited states were compared with the theoretical electric dipole oscillator strengths calculated from the
Judd-Ofelt [Phys. Rev. 127, 750 (1962)
;
J. Chem. Phys. 37, 511 (1962)
] theory. The emission cross sections and gain cross sections of the π and σ spectra were determined for the → transition of special interest for laser application.
Journal of Applied Physics 08/2006; 100(3):033103-033103-5. · 2.17 Impact Factor
