Numerical investigation of gain characteristics of Er3+/Yb3+ co-doped fiber amplifiers

In this work, a model for analyzing the gain characteristics of heavily Er³⁺/Yb³⁺ co-doped compact fiber amplifier is presented. Four-level rate equations and finite-difference beam propagation method are applied to simulate the optical field evolution along the active fiber. Based on this model, the influences of ion concentration, fiber length and pump power on the gain characteristics of Er³⁺/Yb³⁺ co-doped phosphate glass fiber amplifiers are theoretically investigated. Numerical results show that for a fiber length of 3.6 cm the internal gain can reach 27.2 dB with N _Er = 2.6 × 10²⁶ ions/m³ and N _Yb = 1.2 × 10²⁷ ions/m³ when pumped with 224 mW at 980 nm. The gain per centimeter is 7.56 dB/cm. The results can provide useful information to optimize the gain performance of these compact fiber amplifiers.     

Analysis for amplifying characteristics of Er-Yb-co-doped microring resonators

Formulas of the transfer functions and the output power gains are presented, amplifying characteristics are analyzed, and simulation is performed for an Er³⁺-Yb³⁺-co-doped microring resonator. Under the pump wavelength of 980 nm and the central signal wavelength of 1550 nm, the dependence of the output power gain on the amplitude coupling ratio, pump power, signal power, and the dopant concentration is investigated, the output spectra are presented, and the optimization of the device is carried out. Simulated results show that the output power gain of this device is much larger than that of the Er³⁺-Yb³⁺-co-doped straight waveguide amplifier (EYCDWA) with the same waveguide parameters.     

Wavelength tunable linear cavity cladding pump Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript>co-doped fiber laser operating in L-band

We have demonstrated a novel tunable linear cavity Er³⁺/Yb³⁺ co-doped fiber laser, which utilizes amplified spontaneous emission as a secondary pump source so that it can operate in L-band. The tuning wavelength range can be up to 34 nm, from 1588.6 to 1622.6 nm, and the output power excursion of the laser at different wavelengths can be less than 0.4 dB by using a two sections of high-birefringence fiber loop mirror as the wavelength filter. The high output power of 200 mW is realized by using the cladding-pump.     

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Yb3+:Er3+:Tm3+ 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 Yb3+,Er3+ and Tm3+ ions are discussed.The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power.The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.     

A numerical method for solving gain characteristics of Er/Yb codoped waveguide amplifiers

By means of the interpolation and iteration methods to deal with the rate equations and the light propagation equations for the Er³⁺/Yb³⁺ codoped waveguide amplifier (EYCDWA), the gain characteristics in the forward, backward, and bidirectional pumped styles are analyzed. In order to obtain high gain, some parameters such as waveguide length, dopant concentration, pump power, and signal power are optimized. The results show that the pump power and signal power are about 50 mW and 1 mW, respectively, the gain is about 6.5 dB for the 2.0 cm-long EYCDWA with an Er³⁺ ion concentration of 1.5 × 10²⁶ m^–3 and Yb³⁺ ion concentration of 1.9 × 10²⁷ m^–3. Moreover, the upconversion is investigated for the designed device.     

Er3+，Er3+/Yb3+掺杂氟化镧超微材料的光谱特性与上转换发光

采用共沉淀法制备了Er³⁺掺杂和Er³⁺/Yb³⁺共掺杂LaF₃超微材料,所制备的样品的颗粒呈球形,尺寸为250nm左右.计算得到Er³⁺单掺杂样品中对应着⁴S_3/2和⁴F_9/2能级的发光量子效率分别为67.0%和71.9%.研究发现,随着Yb³⁺离子浓度的增加 关键词： 3+')" href="#">Er³⁺ 3+')" href="#">Yb³⁺ 发光 能量传递     

高浓度镱铒共掺磷酸盐光纤放大器增益特性

在忽略高能级的自发辐射和光纤损耗的情况下，利用速率方程和传输方程理论研究了高浓度Er³⁺/Yb³⁺共掺磷酸盐玻璃光纤放大器的增益特性，讨论了Er³⁺浓度、Yb³⁺浓度、抽运光功率、信号光功率、光纤长度对放大器增益的影响，并与单掺铒光纤放大器进行了比较.由于Yb³⁺的敏化作用降低了铒离子的团簇效应，减少了离子间相互作用，共掺光纤的增益和效率明显高于单掺光纤.数值计算表明，3.2cm长Er³⁺/Yb³⁺共掺光纤在980nm的20dBm(100mW)抽运功率下，1532nm处的增益可达10dB. 关键词： 镱铒共掺光纤放大器 速率方程 传输方程 高浓度     

Yb3+sensitized Er3+-doped waveguide amplifiers: a theoretical approach

Silicate and phosphate glass waveguide amplifiers doped with Er³⁺, and co-doped with Er³⁺/Yb³⁺ are theoretically studied. Configurations for core and core–cladding doped waveguide amplifiers are considered. It is shown that gain in the core–cladding doped amplifiers is considerably higher than core doped amplifiers. It is also shown that with input signal power up to 1 and 200mW pump power, a 12.5dB gain can be achieved in a 3cm long waveguide amplifier, with a noise figure of 3dB.     

Upconversion properties of Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glasses

The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb^3＋/Er^3＋ is discussed in detail, and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb^3＋/Er^3＋ is also studied, The luminescence intensity increases with the ratio of Yb^3＋/Er^3＋ increasing. The ratio of Yb^3＋/Er^3＋ plays a more important role than the concentration of Er^3＋ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb^3＋/Er^3＋ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.     

共沉淀法制备Y2SiO5∶Er3+ ,Yb3+ ,Tm3+及其上转换发光性能研究

采用化学共沉淀法制备了系列Y_1.98-2xYb_2x Er_0.02SiO₅(0.00≤x≤0.15)以及Y_1.736Yb_0.24Er_0.02Tm_0.004SiO₅上转换发光材料,比较了室温下Y_1.98-2xYb_2x Er_0.02 SiO₅ (x=0.00,0.08)样品在400—1600 nm范围内的吸收光谱,测量了所有样品在976 nm OPO激光器激发下的上转换发射光谱,以及Er³⁺离子⁴S_3/2(⁴F_9/2)→⁴I_15/2,Tm³⁺离子¹G₄→³H₆荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er³⁺,Tm³⁺在Y₂SiO₅中的上转换发光机理.研究结果表明:在1250 ℃相对较低的温度下合成了X2型单斜晶系Y₂SiO₅ ∶Ln³⁺(Ln³⁺=Er³⁺,Yb³⁺,Tm³⁺),Yb³⁺的敏化显著增强了样品在976 nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb³⁺浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er³⁺→Yb³⁺反向能量传递ETU4和Yb³⁺→Er³⁺正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb³⁺,Tm³⁺之间三次声子辅助的能量转移方式实现的. 关键词： 上转换 共沉淀 2SiO₅∶Er³⁺')" href="#">Y₂SiO₅∶Er³⁺ 3+')" href="#">Yb³⁺ 3+')" href="#">Tm³⁺     

The up-conversion properties of Yb and Er doped Y4Al2O9 phosphors

Er³⁺ doped and Yb³⁺/Er³⁺ co-doped Y₄Al₂O₉ phosphors are prepared by the sol-gel method. The effect of dopant concentration on the structure and up-conversion properties is investigated by X-ray diffraction (XRD) and photoluminescence, respectively. XRD pattern indicates that the sample structure belongs to monoclinic. Under 980 nm excitation, the green and red up-conversion emissions are observed and the emission intensities depended on the Yb³⁺ ion concentration. The green up-conversion emissions decrease with the increase of Yb³⁺ concentration, while red emission increases as Yb³⁺ concentration increases from 0 to 8 at% and then decreases at high Yb³⁺ concentration. The mechanisms of the up-conversion emissions are discussed and results shows that in Er³⁺ and Yb³⁺/Er³⁺ co-doped system, cross-relaxation (CR) and energy transfer (ET) processes play an important role for the green and red up-conversion emissions.     

Optical parameters of Nd3＋：Er3＋：yb3＋ co-doped borosilicate glasses and their energy transfers at high temperature

This paper reports that a series of Nd³⁺:Er³⁺:Yb³⁺ co-doped borosilicate glasses have been prepared and their absorption spectra measured. The J--O intensity parameters Ω_k (k=2, 4, 6), spontaneous radiative lifetime τ_rad, spontaneous transition probability A, fluorescence branching ratio β and oscillator strength f_ed of the Nd³⁺ ions at room temperature are calculated based on Judd--Ofelt (J--O) theory. The temperature dependence of the up-conversion photoluminescence characteristics in a Nd³⁺:Er³⁺:Yb³⁺ co-doped sample is studied under a 978 nm semiconductor laser excitation, and the energy transfer mechanisms among Yb³⁺, Er³⁺ and Nd³⁺ ions are analysed. The results show that the J--O intensity parameters Ω₂ increase when the Nd³⁺ concentration of the Nd³⁺:Er³⁺:Yb³⁺ co-doped borosilicate glasses increases. The possibility of spontaneous transition is small and lifetimes are long at levels of ⁴F_5/2 and ⁴F_3/2. The intensity of Nd³⁺ emissions at 595, 691, 753, 813 and 887 nm are markedly enhanced when the sample temperature exceeds 400 K. The reasons being the cooperation of the secondary sensitization from Er³⁺ to Nd³⁺ and the contribution of a multi-phonon.     

Enhancement of upconversion luminescence in Tm/Er/Yb-codoped glass ceramic containing LiYF4 nanocrystals

A transparent Er³⁺–Tm³⁺–Yb³⁺ tri-doped oxyfluoride glass ceramics containing LiYF₄ nanocrystals were prepared. Under 980 nm laser diode (LD) pumping, intensive red, green and blue upconversion (UC) was obtained. The blue, green, and red UC radiations correspond to the transitions ¹G₄→³H₆ of Tm³⁺, ²H_11/2/⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2 of Er³⁺ ions, respectively. This is similar to that in Tm³⁺–Yb³⁺ and/or Er³⁺–Yb³⁺ co-doped glass ceramics. However, the blue UC radiations of the Er³⁺–Yb³⁺ co-doped glass ceramics is two-photon process due to cooperative energy transfer. The UC mechanisms were proposed based on spectral, kinetic, and pump power dependence analyses.     

全光纤超短脉冲掺Yb3+光纤环形激光器

讨论了自启动被动锁模掺Yb³⁺光纤环形激光器产生短脉冲的机理，并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.采用两个976nm半导体激光器级联抽运作为抽运源，高掺杂浓度掺Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到自启动、十分稳定的ps量级锁模光脉冲.激光器锁模阈值功率260mW，输出功率25mW，锁模光脉冲中心波长1056nm，3dB带宽11.7nm，重复频率20MHz.与其他结构光纤激光器相比，这种全光纤结构具有更高的效率和更好的稳定性. 关键词： 环形光纤激光器 3+光纤')" href="#">高掺杂浓度掺Yb³⁺光纤 自启动 被动锁模     

Yb3+敏化的Er3+/Ho3+共掺碲酸盐玻璃的上转换发光研究

用高温熔融法制备了系列Er³⁺/Yb³⁺共掺，Ho³⁺/Yb³⁺共掺，和Er³⁺/Yb³⁺/Ho³⁺三掺碲酸盐玻璃，在975nm激光抽运下三种掺杂玻璃中都出现了较强的绿光和红光上转换.研究了Yb³⁺离子对Er³⁺和Ho³⁺离子上转换发光强度的影响以及Yb³⁺→Er关键词： 3+/Yb³⁺/Ho³⁺共掺')" href="#">Er³⁺/Yb³⁺/Ho³⁺共掺 碲酸盐玻璃 光谱性质 上转换     

Study on up-conversion emissions of Yb/Tm co-doped GdF3 and NaGdF4

The Yb³⁺/Tm³⁺ co-doped GdF₃ and NaGdF₄ samples were synthesized through a combination method of a co-precipitation and an argon atmosphere annealing procedures. X-ray diffraction analysis indicated that the Yb³⁺/Tm³⁺ co-doped GdF₃ sample crystallized well and was orthorhombic phase, and the Yb³⁺/Tm³⁺ co-doped NaGdF₄ sample was hexagonal phase. With a 980-nm semiconductor continuous wave laser diode as the excitation source, the up-conversion emission spectra of the two samples in the wavelength range of 240-510 nm were recorded. In the up-conversion emissions of the samples, Yb³⁺ transferred energies to Tm³⁺ resulting in their ultraviolet, violet, and blue up-conversion emissions. And, Tm³⁺ simultaneously transferred energies to Gd³⁺, which finally resulted in ultraviolet up-conversion emissions of Gd³⁺. The study on the excitation power dependence of up-conversion fluorescence intensity indicated that there were multi-photon (three-, four-, five-, and six-) processes in the up-conversion emissions of the samples. And the up-conversion emissions of Gd³⁺ and Tm³⁺ in the Yb³⁺/Tm³⁺ co-doped GdF₃ and NaGdF₄ samples were compared studied, too.     

NIR to visible upconversion in Er/Yb co-doped CaYAl3O7 phosphor obtained by solution combustion process

Using the combustion synthesis, CaYAl₃O₇:Er³⁺ phosphor powders co-doped with Yb³⁺ have been prepared at low temperatures (550 °C) in a few minutes. Formation of the compound was confirmed by X-ray powder diffraction. Near-infrared to visible upconversion fluorescence emission in the Er³⁺ doped CaYAl₃O₇ phosphor powder has been observed. The effect of co-doping with triply ionized ytterbium in the CaYAl₃O₇:Er³⁺ phosphor has been studied and the process involved is discussed.     

Optical character of Er/Yb co-doped P2O5-CaO-Na2O-Al2O3-AgO phosphate glass

The up-conversion (UC) and near infrared (NIR) luminescence of Er³⁺/Yb³⁺ co-doped phosphate glass are investigated. In the UC emission range, the 523 nm, 546 nm green emissions and the 659 nm red emission are observed. With the increasing pump power, the intensity ratios of I₅₂₃/I₆₅₉, I₅₄₆/I₆₅₉ and I₅₂₃/I₅₄₆ increase gradually. The phenomenon is reasonably interpreted by theoretical analysis based on steady state rate equations. The emission cross section of the infrared emission at 1546 nm is larger (about 6.7 × 10^− 21 cm²), which is suitable for making fiber amplifier.     

Spectral beam combining of fiber lasers based on a transmitting volume Bragg grating

Based on the principle of spectral beam combining using a transmitting volume Bragg grating, a simple experimental setup was designed, in which an approach to control the incidence angles of beams using a focusing lens is presented. The experimental results for the spectral beam combining of two fiber lasers are reported. The gain media used in this experiment were large-mode area Er³⁺/Yb³⁺ co-doped double-clad fibers, pumped by semiconductor lasers. The output powers of the two fiber lasers were 0.39 and 0.53 W, respectively. With a grating diffraction efficiency of about 60%, a maximum combined power of 0.64 W with an absolute combining efficiency of about 69.6% was achieved.     

铒镱共掺光波导激光器的稳态特性

从光波导激光器的工作理论出发,研究了铒镱共掺磷酸盐波导激光器的稳态特性。利用重叠因子简化了980 nm光抽运的铒镱共掺波导激光器四能级模型的速率-传输方程;在忽略自发辐射的情况下,利用数值模拟的方法,得到了铒镱共掺波导激光器的输出与Er³⁺/Yb³⁺离子浓度、泵浦功率、波导长度等参量之间的关系曲线。理论分析结果表明,选择合适的铒镱离子浓度是制作铒镱共掺波导激光器的关键。采用980 nm波长的泵浦光,泵浦功率为80 mW,Er³⁺浓度取20×10²⁶/m³左右,Yb³⁺/Er³⁺浓度比为7~10,波导长度为20 cm左右时,可以得到最大输出光功率。