高功率宽带掺铒超荧光光源

采用单程后向结构,通过优化掺铒光纤的长度及抽运功率等参量,并尽量提高熔接效率,实现了一种功率达28.58mW(14.56dBm)的高功率宽带光源,在1525-1565nm之间功率高达27.34mW(14.37dBm)。在未加任何滤波器的情况下,其3dB带宽为31.2nm。对一根光纤中前向与后向光光谱特点进行分析比较。结果表明,用一段光纤和一只二极管可实现C L波段的宽带高功率光源,结构紧凑,成本低。     

Polarized erbium-doped superfluorescent fiber source utilizing double-pass backward configuration

An erbium-doped superfluorescent fiber source utilizing a double-pass backward configuration is analyzed when a polarizer is inserted into an erbium-doped fiber to obtain polarized output light. Such a polarized configuration is simulated and experimentally confirmed to have the following characteristics: high polarization power conversion efficiency, pump-power-independent mean-wavelength operation, and low sensitivity to polarizer insertion loss.     

晶体结构对Er/Yb共掺ZnO薄膜光致荧光特性的影响

采用脉冲磁控溅射技术制备了Er/Yb共掺ZnO薄膜,对不同退火温度下薄膜晶体结构和光致荧光(PL)光谱进行了系统分析,探讨了退火处理所导致的晶体结构变化以及反应新相的生成对Er3+离子激活、薄膜PL光谱的影响.研究结果表明,退火处理所导致的Er3+离子PL光谱的变化与薄膜的微观状态之间有着密切的联系.在室温到1050℃退火温度范围内,Er/Yb共掺ZnO薄膜为多晶结构,薄膜荧光强度的增加主要是薄膜内氧含量增加、缺陷减少使Er3+离子荧光寿命增加以及Er3+离子激活比例增加所致.当退火温度超过1050℃,荧光强度的明显降低是由新相生成造成缺陷增加以及薄膜内氧含量降低引起.在整个退火温度范围内,薄膜的PL光谱都表现为同一种光谱特性,即明锐的多峰结构,这说明Er3+在ZnO和Zn2SiO4中的周围环境非常相似.     

高功率双包层Er3+/Yb3+共掺光纤放大器的动态响应

基于速率方程的离散算法,分析了双包层Er3 /Yb3 共掺光纤放大器的动态响应,显示了输出功率和增益的动态特征。当单个脉冲注入放大器时,输出脉冲的峰值功率不仅依赖于输入脉冲的峰值功率,而且依赖于泵浦功率;当脉冲序列注入时,输出脉冲的功率和增益最终将收敛于它们的稳态值。在双信道情况下,输入脉冲重叠时的输出功率和增益变得更陡峭。在连续波泵浦下,反向自发辐射输出功率(ASE-)首先快速地增加到峰值功率,然后单调下降到稳态值;在脉冲波泵浦下,反向自发辐射输出功率(ASE )与光纤长度成反比,而ASE-与光纤长度成正比。     

Measurement of gain tilt and its contribution to composite second-order distortion in the analog-digital transmission systems with Er/Yb fiber amplifiers

Fiber-optic-based analog or digital community antenna television systems experience composite second-order (CSO) distortion caused by the interaction between the gain tilt of the doped fiber amplifier and the laser chirp due to modulation. The gain tilt for an analog-digital transmission system with a high-power erbium/ytterbium-codoped fiber amplifier has been experimentally measured and its contribution to the CSO distortion of the system is evaluated. The results are in good agreement when compared with the direct measurement of the CSO distortion of the transmission system with and without the amplifier. The dependence of the gain tilt on the modulation frequency and wavelength of the input light is also investigated.     

Efficient two-color luminescence of Er/Yb/Li:ZrO2 nanocrystals

We demonstrate the upconversion-photoluminescence spectra of Er³⁺, Yb³⁺ and Li⁺ ions doped ZrO₂ nanocrystals. By introducing Li⁺, emission intensities of single green and single red band increase by a factor of 1.93 and 1.65, respectively. Powder X-ray diffraction data and decreased slopes of the excitation power dependences on upconverted emission intensities give evidences that Li⁺ ions can tailor the local structure of host lattice and improve energy transfer processes from Yb³⁺ to Er³⁺, respectively.     

Fiber-optic gyroscope with suppression of excess noise from the radiation source

A new optical system is proposed and investigated experimentally for a Sagnac fiber interferometer in which the excess noise of the wide-band radiation source is suppressed. A tenfold improvement in the sensitivity of a fiber-optic gyroscope with an erbium/ytterbium fiber superfluorescent light source was achieved experimentally. It is shown that the identity of the polarization characteristics of the interferometer channels plays an important role. Pis’ma Zh. Tekh. Fiz. 24, 30–35 (September 26, 1998)     

Yb to Er energy transfer and rate-equations formalism in the eye safe laser material Yb:Er:Ca2Al2SiO7

Rate equations formalism is used to predict the population ratio of the Er^{3+ 4}I_13/2 levels involved in the 1.55 μm laser transition in the Yb:Er:CAS laser materials. An effective Yb → Er energy transfer, favourable to the Er³⁺ 1.55 μm laser emission, is demonstrated in this laser host. Indeed, the Yb → Er transfer and the Er → Yb back transfer rates are calculated to be 6 x 10⁻¹⁶ and 0.45 x 10⁻¹⁶ cm³ s⁻¹, respectively. Attempts of codoping the system with Nd³⁺, Eu³⁺ and Ce³⁺ have been realised in order to increase the population of the Er^{3+ 4}I_13/2 laser emitting level. Best results are obtained with Ce³⁺ ion since in the sample containing 6 x 10²⁰ Ce³⁺/cm³, the Er^{3+ 4}I_11/2 level lifetime is divided by a factor of 3 while the Er^{3+ 4}I_13/2 fluorescence lifetime remains unaffected. On the contrary, codoping with Nd³⁺ or Eu³⁺ ions simultaneously decreases the Er^{3+ 4}I_11/2 and ⁴I_13/2 kinetics parameters. The role of the other parameters such as Yb/Er concentrations ratios is also discussed.     

Preparation and upconversion property of TeO2:Er/Yb nanoparticles

Different crystal structure of TeO₂ nanoparticles were used as the host materials to prepare the Er³⁺/Yb³⁺ ions co-doped upconversion luminescent materials. The TeO₂ nanoparticles mainly kept the original morphology and phase after having been co-doped the Er³⁺/Yb³⁺ ions. All the as-prepared TeO₂:Er³⁺/Yb³⁺ nanoparticles showed the green emissions (525 nm, 545 nm) and red emission (667 nm) under 980 nm excitation. The green emissions at 525 nm, 545 nm and red emission at 667 nm were attributed to the ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions of the Er³⁺ ions, respectively. For the α-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles, three-photon process involved in the green (²H_11/2 → ⁴I_15/2) emission, while two-photon process involved in the green (⁴S_3/2→⁴I_15/2) and red (⁴F_9/2 → ⁴I_15/2) emissions. For the β-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles, two-photon process involved in the green (²H_11/2 → ⁴I_15/2), green (⁴S_3/2 → ⁴I_15/2) and red (⁴F_9/2 → ⁴I_15/2) emissions. It suggested that the crystal structure of TeO₂ nanoparticles had an effect on transition processes of the Er³⁺/Yb³⁺ ions. The emission intensities of the α-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles and β-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles were much stronger than those of the (α + β)-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles.     

Sequence lasing in a gain-switched Yb3+,Er(3+)-doped silica double-clad fiber laser

Experimental results relating to the gain-switched operation of a double-clad Yb3+,Er(3+)-doped silica fiber laser that is pulse pumped with the output from a flash-lamp-pumped Ti:sapphire laser are presented. For all the configurations of the fiber laser that we studied, the 2F5/2-->2F7/2 laser transition of the Yb3+ ion lased prior to laser emission from the 4I13/2-->4I15/2 transition of the Er3+ ion. To the best of our knowledge, this is the first reported operation of sequence lasing in the Yb3+,Er(3+)-codoped system. This succession of laser pulses deduced from the measurements of this investigation is a consequence of both the short intense pump pulse and the short 900-nm wavelength of the pump that does not overlap with any important excited-state absorption transitions. We believe that the predominant interionic interaction during the course of the pump pulse is the double-energy transfer to the Er3+ ion acting twice from the 2F5/2 energy level of the Yb3+ donor ion. A maximum total output of 1.65 mJ is obtained (1.38 mJ from the 2F5/2-->2F7/2 transition of Yb3+ and 0.27 mJ from the 4I13/2-->4I15/2 transition of Er3+) from a nonoptimized configuration of the fiber laser. The wavelength of the output from the fiber laser was measured to vary approximately linearly with fiber length from 1040 to 1046 nm for the Yb(3+)-based laser and 1535 to 1541 nm for the Er(3+)-based laser.     

Synthesis of BaMoO4:Er/Yb particles by an MAM method and their upconversion photoluminescence properties

Er³⁺-doped BaMoO₄ (BaMoO₄:Er³⁺) and Er³⁺/Yb³⁺ co-doped BaMoO₄ (BaMoO₄:Er³⁺/Yb³⁺) particles were successfully synthesized by a cyclic microwave-assisted metathetic (MAM) method, and show fine and homogeneous morphology with particle sizes of 0.5–1 μm. At 980-nm excitation, BaMoO₄:Er³⁺ and BaMoO₄:Er³⁺/Yb³⁺ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region. The Raman spectrum of BaMoO₄:Er³⁺/Yb³⁺ particles indicated the appearance of additional peaks at higher frequencies (390 and 505 cm⁻¹) and at lower frequencies (218 and 255 cm⁻¹).     

The effect of In ion on the optical characteristics of Er in Er/Yb:LiNbO3 crystal

The effect of In³⁺ ion on the optical characteristics of Er³⁺ ion in Er/Yb:LiNbO₃ crystal under 980 nm excitation has been investigated. The Er and Yb contents in the crystals were measured by an inductively coupled plasma atomic emission spectrometer (ICP-AES). A significant enhancement of 1.54 μm emission was observed for Er/Yb:LiNbO₃ crystal doped with 1 mol% In₂O₃. The studies on the UV-vis absorption and the OH⁻ absorption spectra indicate that the threshold concentration of In³⁺ ion decreases with the Er/Yb doping in Er/Yb/In:LiNbO₃ crystal. The 1 mol% In₂O₃ doping results in the reduction of absorption cross section in the UV-vis region, meaning the formation of Er³⁺ cluster sites. The enhancement of 1.54 μm emission is attributed to the larger probabilities of the cross relaxation processes ⁴S_3/2 + ⁴I_15/2 → ⁴I_9/2 + ⁴I_13/2 (Er), ⁴S_3/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_9/2 (Er) and ⁴I_9/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_13/2 (Er) induced by Er³⁺ cluster sites.     

Flame synthesis and effects of host materials on Yb/Er co-doped upconversion nanophosphors

The upconversion nanophosphors (UCNPs) of Yb³⁺/Er³⁺ co-doped into Y₂O₃, La₂O₃, and Gd₂O₃ were synthesized via the combustion method and characterized by powder X-ray diffractometer (XRD), scanning electron microscopy (SEM) and upconversion fluorescence spectroscopy. The characterization results showed that at the same flame temperature (2705 K) and precursor concentration (0.1 M), pure monoclinic and cubic-phase phosphors were achieved on Gd₂O₃ and Y₂O₃ hosted UCNPs, respectively; while the mixed phases were observed on La₂O₃ hosted UCNPs. Further annealing process at 850 °C produced pure cubic-phase La₂O₃:Yb³⁺,Er³⁺ UCNPs; while there was no phase transition observed on Gd₂O₃:Yb³⁺,Er³⁺ UCNPs. The dependence of upconversion luminescence on precursor concentrations and host materials was then examined. The La₂O₃ and Gd₂O₃ hosts were shown to be the promising alternates for the commonly used Y₂O₃ hosts for rare-earth doped phosphors.     

Temperature dependence of luminescence behavior in Er/Yb co-doped transparent phosphate glass ceramics

The effect of temperature on the luminescence intensity of up-conversion and near infrared in Er³⁺/Yb³⁺ co-doped phosphate glass ceramics has been investigated. Efficient green and red up-conversion luminescence and strong infrared fluorescence at 1.54 μm wavelength are observed under excitation of 975 nm. The fluorescence intensity is changing at different temperature and the results are explained with the level transitions in Er³⁺/Yb³⁺ co-doped system. Meanwhile, the lifetime of Er³⁺:⁴I_13/2 level corresponding to different operating temperature and pump power is also discussed, and the experimental results are fitted using multiphonon relaxation theory.     

Multi-photon luminescence in Er/Yb:SrO⋅TiO2 glass ceramic

Er³⁺/Yb³⁺ doped strontium titanate borosilicate glass was prepared. Glass ceramic was prepared by controlled heat treatment (at 955 °C) of glass. Ti₁₀O₁₉ and Sr₃Ti₂O₇ were found as major crystalline phases. The emission spectra of glass and glass ceramic samples were investigated under 976 nm laser excitation. In glass ceramic, the intensity of the emitted radiation was much higher (≈50 times for green and ≈10 times for red emission) than in the glass. A new three photon process was found to be responsible for emission at low power which is not yet observed in Er³⁺/Yb³⁺:SrO⋅TiO₂ glass ceramic system to the best of our knowledge. The details of upconversion mechanisms e.g. Energy Transfer (ET) and Excited State Absorption (ESA) were studied by power-intensity log dependence. It is expected that Er³⁺/Yb³⁺ doped nanocrystalline (?10 nm) Sr₃Ti₂O₇ phase was responsible for the observed upconversion phenomenon in glass ceramic.     

Single-pulse measurement of wind velocities using an Er:Yb:glass coherent laser radar

Many wind-field mapping applications require range-resolved atmospheric velocity measurements at long range and/or with a temporal resolution sufficient to investigate turbulence. We argue that this capability can be achieved only by coherent laser radar systems that transmit energetic (>1 mJ) pulses. We describe such a system and describe single-pulse measurement of the range-resolved line-of-sight velocities, and show that the instrument-limited reproducibility of the measurements is 0.4 ms(-1).     

晶体结构对Er/Yb共掺TiO2薄膜荧光光谱的影响

通过对不同退火温度下Er/Yb共掺TiO2薄膜的结构和光致荧光光谱(PL)的分析,研究了退火处理所导致的晶体结构变化对薄膜荧光光谱的影响,探讨了薄膜的结晶状态在Er3+激活、荧光光谱形状等方面的作用及可能的物理机制.研究结果表明:退火处理所导致的Er3+的PL的变化与薄膜的相结构之间有着密切的联系.退火温度低于700C时的宽化谱和Er/Yb共掺TiO2薄膜的非晶结构有关,多峰结构的PL是Er3+在烧绿石相ErxYb2-xTi2O7中的典型特征.     

Up-conversion emission in KGd(WO4)2 single crystals triply-doped with Er/Yb/Tm, Tb/Yb/Tm and Pr/Yb/Tm ions

Triply-doped single crystals KGd(WO₄)₂:Er³⁺/Yb³⁺/Tm³⁺, KGd(WO₄)₂:Tb³⁺/Yb³⁺/Tm³⁺ and KGd(WO₄)₂:Pr³⁺/Yb³⁺/Tm³⁺ were grown by the Top Seeded Solution Growth (TSSG) method, with an aim of getting efficient up-converted multicolored luminescence, which subsequently can be used for generation of white light. Such an aim determined the choice of the triply doped compounds: excitation of the Yb³⁺ ions in the infrared spectral region is followed by red, green and blue emission from other dopants. It was shown that all these systems exhibit multicolor up-conversion fluorescence under 980 nm laser irradiation. Detailed spectroscopic studies of their absorption and luminescence spectra were performed. From the analysis of the dependence of the intensity of fluorescence on the excitation power the conclusion was made about significant role played by the host’s conduction band and other possible defects of the KGd(WO₄)₂ crystal lattice in the up-conversion processes.     

高发光效率的亲水性NaYF4:Yb/Er纳米晶的制备

以不同比例的乙二醇和水作为混合溶剂,稀土氯化物和NaF为反应物,采用简易的溶剂热法一步制备出亲水性的NaYF4:Yb/Er纳米晶.用透射电子显微镜、X射线粉末衍射、红外吸收以及发光光谱等测试方法对产物的形貌、物相结构、表面配体和荧光性能进行了表征.结果表明,制备的纳米晶形貌比较均一,主要为立方相和六方相的混合相.随着溶剂中含水量由0%增加到50%,纳米晶尺寸变大,六方相NaYF4:Yb/Er含量增加,纳米晶的发光强度增加;进一步增加含水量时,尽管纳米晶尺寸变大,六方相含量也相应增加,但是其发光强度降低,可能是由于配体减少引起纳米晶表面缺陷增加,导致发光淬灭.     

Luminescence of Yb, Yb co-doped silica glass for white light source

Yb²⁺, Yb³⁺ co-doped silica glasses were prepared by solid state reaction under vacuum condition for the first time. The luminescence properties of Yb²⁺-doped silica glass were investigated. There are four strong absorption bands in the Ultraviolet (UV) light region due to the 4f¹⁴-4f¹³5d¹ transition of the Yb²⁺ ions. The main emission wavelength of the Yb²⁺-doped silica glass was around 530 nm by the excited wavelength of 398 nm. The full width at half maximum (FWHM) of the excitation and emission bands were 137 nm, 165 nm respectively. The results suggest the Yb²⁺-doped silica glasses may be the potential medium for white light sources based on near UV LED chip.