Up-conversion luminescence properties and energy transfer of Er^(3+)/Yb^(3+)co-doped oxyfluoride glass ceramic containing CaF_2 nano-crystals

The Er^3＋/yb^3＋ co-doped transparent oxyfluoride glass-ceramics containing CaF2 nano-crystals were successfully prepared. After heat treatments, transmission electron microscopy （TEM） images showed that CaF2 nano-crystals of 20-30 nm in diameter precipitated uniformly in the glass matrix. luminescence of Er^3＋ at 540 nm and 658 nm was observed in Comparing with the host glass, high efficiency upconversion the glass ceramics under the excitation of 980 nm. Moreover, the size of the precipitated nano-crystals can be controlled by heat-treatment temperature and time. With the increase of the nano-crystal size, the intensity of the red emission increased more rapidly than that of the green emission. The energy transfer process of Er^3＋ and Yb^3＋ was convinced and the possible mechanism of Er^3＋ up-conversion was discussed.

Optical temperature sensor based on up-conversion fluorescence emission in Yb^(3+):Er^(3+) co-doped ceramics glass

yb^3＋：Er^3＋ co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er^3＋ was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K^-1, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

Spectral and Lasing Properties of Er^(3+0/Yb^(3+) Co-Doped Phosphate Glasses Pumped by LD

Er^3 ＋/Yb^3 ＋ phosphate glasses were fabricated. According to McCumber theory, the stimulated emission cross-section of Er^3＋ ions at 1533 nm was calculated on the basis of absorption spectrum, and 0.84 × 10^-20 cm^2 is derived, the fluorescence lifetime of ^4I13/2 level is 8.5 ms. An Er^3＋/Yb^3＋ co-doped phosphate glass CW laser pumped by LD was demonstrated at room temperature. The maximum output power is 80 mW and slope efficiency is 16.5%.

Up-conversion photoluminescence characteristics of Yb^(3+):Er^(3+):Tm^(3+) co-doped borosilicate glasses

Yb^3＋：Er^3＋：Tm^3＋co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb^3＋ Er^3＋ and Tm^3＋ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb^3＋ Stark splitting levels to pump Tm^3＋ ions and there exists an optimum pump power. The concentration of the Tm^3＋ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the yb^3＋：Er^3＋：Tm^3＋ co-doped borosilicate glasses.

All-fiber Based Er^(3+)∶Yb^(3+) Co-doped Fiber Laser

An all-fiber based Er~ 3+ ∶Yb~ 3+ co-doped double clad fiber laser operating at 1550nm is demonstrated. By using 9m long Er~ 3+ ∶Yb~ 3+ co-doped fiber(EYDF) as the gain medium, and using a pair of fiber Bragg gratings as wavelength filters, the line-width of the output laser is as narrow as 0.2nm and the output power is more than 6mW. The fluorescent effect of the laser before its emission is also studied. And it is found that the Er~ 3+ ∶Yb~ 3+ co-doped double-clad fiber laser also exhibits a high gain for Yb~ 3+ transition near 1080nm.

Influence of Input Pulse Durations on Properties of Er^(3+)/Yb^(3+) Co-doped DCFA

Based on propagation-rate equations, the influence of different input pulse durations on the properties of Er^3＋/Yb^3＋ co-doped double-clad fiber amplifier at dynamic equilibrium was analyzed. The change characteristic of output power sag with pulse duration and repetition rate was shown. Whether single or multichannel input pulses are amplified, the shorter the input pulse duration is, the smaller the power sags of output pulse will be. At low repetition rate, upper gain values（Gupper） of gain swing are almost the same for different input pulse durations, which tend to the small signal gain, but lower gain value（Glower） of short input pulse is larger than that of long input pulse. At highrepetition rate, lower gain value（Glower） approaches to upper gain value（Glower）.

Er^(3+)／Yb^(3+)共掺LiNbO_(3+)晶体中Er^(3+)的光谱特性分析

在室温下,测量了采用Czochralski方法生长的as-grown和经退火处理的Z切Er3+／Yb3+共掺同成 分LiNbO3晶体的a偏振吸收光谱(300-1 650 nm)。运用Judd-Ofelt理论对该晶体中Er3+的光谱特性进行 了分析。由所测得的吸收系数的积分计算得到了从基态到激发态的若干个主要的电子跃迁强度实验值。利 用最小二乘法确定出Er3+／Yb3+共掺LiNbO3晶体中Er3+的Judd-Ofelt参数。进而确定了自发辐射概率,从 激发态能级到其各个下能级的荧光分支比以及能级辐射寿命。此外,还讨论了Yb3+的共掺和退火处理对 LiNbO3晶体中Er3+光谱特性的影响。

Spectral Properties and Upconversion Luminescence of Er^(3+),Yb^(3+):BaWO_4 Crystal

The optical quality of Er^3＋, yb^3＋： BaWO4 crystal was gown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er^3＋ ion were fitted to beΩ2 =0.3926 x 10^-20 cm^2, Ω4 =0.0721×10^-20 cm^2, Ω6 =0.0028 ×10.20 cm^2. Emission peaks centered at around 523,544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.

Growth and Optical Spectra of Zn∶Er∶LiNbO_3 Crystals Using Bridgman Method

The growth of LiNbO3 single crystal with Er^3＋ and Zn^2＋ co-doped using Bridgman method and its characteristic absorption spectra and fluorescence spectra were reported. Large-size crystals initially containing Zn^2＋ （3%） and Er^3＋ （0.6%） with good optical quality were obtained using optimized conditions such as a growth rate of 0.8- 1.5 mm·h^-1 and a temperature gradient of about 30 - 35℃·cm^-1 across the solid-liquid interface and the sealed platinum crucible. X-ray diffraction and differential thermal analysis （DTA） were used to characterize the crystals. The results indicate that the concentration of Er^3＋ ions in crystals, their absorption intensity, and their fluorescence intensity decrease from the bottom to the top in the crystals. However, for the upper part of the crystal, the up-conversion fluorescence intensity is higher than that of the lower part excited by an 800 or 970 nm pump. The effects of the crystal lattice, their structural defect and their effective segregation of Er^3＋ ions were discussed with respect to the variations of the up-conversion fluorescence intensity.

Growth and Optical Spectra of Zn∶Er∶LiNbO_3 Crystals by Bridgman Method

The growth of LiNbO3 single crystal with Er^3＋/Zn^2＋ co-doped by the bridgman method and the characteristics of absorption spectra and fluorescence spectra were reported. By means of the optimized con- ditions such as growth rate of 0.8 - 1.5 mm · h^- 1, temperature gradient about 30 - 35℃ ·cm^-1 across the solid-liquid interface and sealed platinum, large size crystals containing Zn^2＋ （3%） and Er^3＋ （0.6%） with good optical quality were obtained. X-ray diffraction and DTA were used to characterize the crystals. The results indicate that the concentration of Er^3＋ ions in crystals decrease along the growth direction, the absorption intensity and the fluorescence intensity ions also decrease along the growth direction. of Er^3＋ However, for the upper part crystal, the upconversion fluorescence intensity is higher than that of the lower part crystal excited with 800 or 970 nm pump. The effects of crystal lattice, structure defect and effective segregation of Er^3＋ ions were discussed in respect to the variations were discussed of upconversion fluorescence intensity.

Near-infrared carbon-implanted Er^3＋/yb^3＋ co-doped phosphate glass waveguides

The Er3＋/yb3＋ co-doped phosphate （EYDP） glass waveguides operated at 1539 nm have been manufactured by using the implantation technique of carbon ions under the condition of 6.0 MeV energy and 5.0 × 10^13 ions/cm2 fluence in this work. The ion implantation process was computed by means of the stopping and range of ions in matter. The dark-mode spectrum at 1539 nm of the waveguide was recorded by the method of the prism coupling measurement. The microscopic image of the fabricated structure was photographed by an optical microscope. It is the first step for the application of the waveguides on the base of EYDP glasses in optical- integrated photonic devices at near-infrared band.

Impact of Yb^(3+)/Er^(3+) ions on crystallization of phosphosilicate glass melts

Transparent glass ceramics were prepared from the phosphosilicate system by melt-quenching devitrification（MQD） method, i.e., nanocrystals spontaneously form during cooling of the melts. Introduction of 2.5 wt.% Yb2O3 and 0.5 wt.% Er2O3 into the glass melt induced the change of type and concentration of crystals. The comparison of rheological and thermodynamic properties of both undoped and Yb^3＋/Er^3＋ doped melts showed that addition of Yb^3＋/Er^3＋ oxides caused increase of liquid fragility, and degree of medium-range order. In addition, the thermodynamic barriers for nucleation ΔG＊ as a function of reduced temperature T/Tm were calculated with an assumption of wetting angle θ=90o, Yb^3＋/Er^3＋ doped melt tended to firstly nucleate as compared to undoped melt at small undercooling.

Upconversion photoluminescence properties of SrY_2O_4:Er^(3+),Yb^(3+) under 1550 and 980 nm excitation

Er^3＋/Yb^3＋ co-doped SrY2O4 phosphors with high color purity and brightness were successfully synthesized via a solid-state reaction method.Luminescence spectrum studies showed that the main red peaks and the minor green peaks of upconversion emissions were located at approximately 634–681 nm and 543–570 nm,respectively,corresponding to the transitions of ~4F（9/2）→~4I（15/2） and ~4S（3/2）→~4I（15/2） of Er^3＋ ions.Under the excitation of 980 and 1550 nm lasers,the spectra of all of the samples exhibited similar peak positions but different intensities.When excited by the 980 nm laser,the intensity ratio of red to green emission increased with increasing Yb^3＋ doping concentration and decreased with increasing excitation power.In the case of 1550 nm excitation,the intensity ratio of red to green emission increased with increasing Yb^3＋ doping concentration and excitation power,thereby,improving the color purity of the red emission.The intensity of red emission was considerably stronger under 1550 nm excitation than that under 980 nm excitation.Therefore,the color of the proposed phosphors could be efficiently tuned by tailoring both the Yb^3＋ doping concentration and excitation power.