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）.

A 301 W narrow-linewidth in-band pumped Er:Yb co-doped fiber amplifier at 1585 nm and related modeling for dynamics study and optimization

To overcome Yb lasing,a kilowatt-level 1535 nm fiber laser is utilized to in-band pump an Er:Yb co-doped fiber(EYDF)amplifier.The output power of a 301 W narrow-linewidth EYDF amplifier operating at 1585 nm,with 3 dB bandwidth of 150 pm and M^(2)<1.4,is experimentally demonstrated.To the best of our knowledge,it is the highest output power achieved in L-band narrow-linewidth fiber amplifiers with good beam quality.Theoretically,a new ion transition behavior among energy levels for in-band pumping EYDF is uncovered,and a spatial-mode-resolved nonlinearityassisted theoretical model is developed to understand its internal dynamics.Numerical simulations reveal that the reduction in slope efficiency is significantly related to excited-state absorption(ESA).ESA has a nonlinear hindering effect on power scaling.It can drastically lower the pump absorption and slope efficiency with increasing pump power for in-band pumped EYDF amplifiers.Meanwhile,optimized approaches are proposed to improve its power to the kilowatt level via in-band pumping.

Noise-like rectangular pulses in a mode-locked double-clad Er:Yb laser with a record pulse energy

Generation of noise-like rectangular pulse was investigated systematically in an Er–Yb co-doped fiber laser based on an intra-cavity coupler with different coupling ratios.When the coupling ratio was 5/95,stable mode-locked pulses could be obtained with the pulse packet duration tunable from 4.86 ns to 80 ns.The repetition frequency was 1.186 MHz with the output spectrum centered at 1.6μm.The average output power and single pulse energy reached a record 1.43 W and1.21μJ,respectively.Pulse characteristics under different coupling ratios(5/95,10/90,20/80,30/70,40/60)were also presented and discussed.

Optimal design of Er/Yb co-doped fiber amplifiers with an Yb-band fiber Bragg grating

In this paper, Er/Yb co-doped fiber amplifiers(EYDFAs) with an Yb-band fiber Bragg grating(FBG) at the pump end to improve the performance of the amplifier is systematically studied. The influence of the reflectivity and center wavelength of the FBG along with the gain-fiber length on the performance of an EYDFA are numerically analyzed. The results show that the wavelength of the FBG has critical influence on the efficiency of the EYDFA,whereas the requirement to its reflectivity is relaxed. It is an effective and promising way to improve the efficiency of a high-power pumped EYDFA by introducing a suitable Yb-band FBG at the pump end. Based on the analysis of the underlying principles, suggestions for the practical design and possible further improvement strategies are also proposed.

高功率Er/Yb共掺光纤脉冲放大器中ASE的影响分析

为了研究自发辐射对高功率铒镱共掺脉冲光纤放大器性能的影响,在速率方程理论的基础上,采用有限差分法对理论模型进行了数值求解。对不同抽运、信号和光纤参量配置情况下,自发辐射对放大器性能的影响进行了模拟分析。结果表明,由于自发辐射自饱和的限制,在其它条件相同的情况下,为了得到最高的单脉冲能量和峰值功率,放大器输入信号存在一个最佳的重复频率,且该最佳重复频率与抽运功率成正比与脉冲宽度成反比。研究结果对高功率铒镱共掺光纤脉冲放大器的设计和实验研究有重要指导意义。

双包层Er^(3+)/Yb^(3+)共掺光纤放大器动态特性研究

基于速率方程的离散算法,实现了对双包层Er3+/Yb3+光纤放大器动态特性的分析。研究了不同信号和泵浦功率下单信道的瞬态功率、脉冲序列输出功率与增益随时间的变化以及多信道异步转移模式下输出功率和增益随时间的变化。结果表明:对于单个脉冲,在相同的泵浦功率下,输出脉冲的峰值功率取决于输入脉冲的峰值功率;在不同的泵浦功率下,输出脉冲的峰值功率取决于泵浦功率。对于脉冲序列,在达到稳定的输出前,将经历一个输出功率和增益由高到低的变化过程。对于异步转移模式的多信道脉冲,脉冲重叠时的功率和增益变化要快于非重叠时功率和增益的变化。

双包层Yb／Er共掺光纤放大器的数值模拟

为优化光纤放大器结构,对980 nm抽运的双包层Yb/Er共掺光纤放大器进行了数值模拟,分析了不同功率下信号光的增益,计算了稳态情况下光纤中的反转粒子数、抽运光功率、信号光功率沿光纤轴向的分布以及放大器的斜率效率。根据数值模拟的结果,采用10 m长的双包层Yb/Er共掺光纤建立了光纤放大器实验装置。最大光纤抽运功率为6 W,初始信号光功率为0.5 W时,获得了1.9 W的最大输出功率,斜率效率为23.4%。

高功率Er/Yb共掺光纤超荧光光源

为了获得高功率超荧光输出,采用6个976nm的LD,通过一个光纤束耦合器同时抽运Er/Yb共掺光纤,分别研究了单程后向结构和双程后向结构超荧光光源的输出特性。采用单程后向装置,当抽运功率为957mW时,输出功率为120.4mW,斜率效率达到17.5%。在双程后向结构的实验装置中加入4m掺Er光纤,有效地将超荧光的3dB带宽拓展到88nm。

双包层Er^(3+)/Yb^(3+)共掺光纤放大器ASE的动态特性

基于速率方程的离散算法,对连续和脉冲泵浦下的双包层Er3+/Yb3+共掺光纤放大器ASE动态特性进行了研究,对ASE随时间呈现不同变化的原因进行了分析。结果表明:连续光泵浦下,双包层Er3+/Yb3+共掺光纤放大器ASE达到稳态的时间和输出功率的大小依赖于泵浦功率,ASE输出功率的增加与Er3+上能级粒子数的减少相对应;脉冲光泵浦下,光纤长度对正向ASE输出功率的饱和存在显著的影响,但不影响反向ASE输出功率的饱和。

Er^(3+)/Yb_(3+)共掺磷酸盐玻璃光纤放大器的增益综述

主要从磷酸盐玻璃光纤的离子掺杂浓度、量子转换效率、信号波长与功率、抽运波长与功率以及光纤长度等方面概述了Er3+/Yb3+共掺磷酸盐玻璃光纤放大器的增益。并简要介绍了国外在该方面的研究进展。

An all-fiber type Er^(3+)/Yb^(3+) co-doped fiber laser

In this paper, a distributed Bragg reflection (DBR) type Er3+/Yb3+ co-doped fiber laser of high output power and high slope efficiency was developed. Its gain medium was a 4.45-m-long Er3+/Yb3+ co-doped fiber. When it was pumped by a 1064-nm Nd:YAG, the linewidth of output laser was measured as 0.072 nm by 3 dB and 0.192 nm by 25 dB at 1552.08 nm. The maximum output power was measured as 69 mW. Its power stability was < 5%, side mode suppression ratio was 59 dB, and the output wavelength stability was +0.01 nm. The laser had a threshold of 12 mW and a slope efficiency of 22%.

Development of Bi/Er co-doped optical fibers for ultra-broadband photonic applications

Targeting the huge unused bandwidth（BW）of modem telecommunication networks,Bi/Er co-doped silica optical fibers（BEDFs）have been proposed and developed for ultra-broadband,high-gain optical amplifiers covering the 1150-1700 nm wavelength range.Ultrabroadband luminescence has been demonstrated in both BEDFs and bismuth/erbium/ytterbium co-doped optical fibers（BEYDFs）fabricated with the modified chemical vapor deposition（MCVD）and in situ doping techniques.Several novel and sophisticated techniques have been developed for the fabrication and characterization of the new active fibers.For controlling the performance of the active fibers,post-treatment processes using high temperature,γ-radiation,and laser light have been introduced.Although many fundamental scientific and technological issues and challenges still remain,several photonic applications,such as fiber sensing,fiber gratings,fiber amplification,fiber lasers,etc.,have already been demonstrated.

Design and Analysis of 120-μm Core Rod-Type Photonic Crystal Fiber for High Power 1.5-μm Band Amplifier

We report the design and analysis of a rod-type photonic crystal fiber with Er-Yb co-doped for the high power 1.5-μm band amplifier.The fiber structure is designed to be the 120-μm extreme large core diameter,300-μm inner cladding diameter,and 1.5-mm outer cladding diameter that ensure the single mode output during high power amplification.Both the continuous wave(CW) and pulsed amplification characteristics are analyzed based on the exact modeling and simulation under the designed geometry.The 4-mJ pulse energy and 400-kW peak power are obtained in theory,so the 1.5-μm band amplifier that achieves milojoule level pulse energy meanwhile keeping single mode is firstly designed.

双包层铒镱共掺光纤放大器功率漂移及控制

基于速率方程的离散算法,分析了双包层Er3+/Yb3+光纤放大器增益动态的特性。研究了功率漂移与撤除信道数的关系及不同控制方式的控制效果。结果表明:信道撤除数量越多,放大器达到稳态的时间越长,功率漂移越大;泵浦控制方式下,泵浦功率的调整随撤除信道数的增加而增大,且抑制功率漂移的时间也随之增长;反馈控制方式下,功率漂移首先呈现振荡结构,抑制功率漂移的时间较短。

高功率脉冲Er-Yb共掺光纤放大器中放大自发辐射的抑制方法

为了研究放大的自发辐射(ASE)对高功率脉冲Er-Yb共掺光纤放大器(EYDFA)的影响,采用数值模拟对EYDFA中不同参数信号的放大进行了研究。结果表明,Yb波段(1.0～1.1μm)ASE是制约放大器输出功率提升的主要因素。因此,有效地抑制Yb波段ASE将有助于放大器性能的提高。通过进一步研究发现,在放大器的抽运端引入一个Yb波段的辅助信号能有效地抑制Yb波段ASE,从而提高抽运转换效率,提升放大器的输出功率。

Er^(3+)-Yb^(3+)共掺磷酸盐玻璃放大器的大信号增益与量子效率理论分析

研究大信号工作状态下的Er3 + Yb3 + 共掺磷酸盐玻璃波导放大器的增益与量子转换效率。从量子转换效率的定义出发 ,得出了增益、抽运光功率以及量子转换效率三者之间关系的解析表达式。通过数值求解大信号工作状态下的Er3 + Yb3 + 共掺系统的速率方程与光功率传输方程 ,讨论了Er3 + 浓度、Yb3 + 浓度、Yb3 + 与Er3 + 浓度比率、抽运光功率以及放大器长度等因素对量子转换效率的影响。结果表明提高Er3 + 浓度与增加放大器长度均有助于提高量子转换效率 ,高Er3 + 浓度掺杂需要相应的高Yb3 + 浓度与之相匹配以减小由于高浓度Er3 + 掺杂引起的上转换效应 ,Yb3 + 浓度的提高将降低器件的量子转换效率 ,Yb3 + Er3 + 浓度之比取 1～ 2较好。

全光纤高功率Er／Yb共掺双包层光纤放大器

结合Er/Yb共掺双包层光纤(EYDCF)和主振荡功率放大(MOPA)技术,采用高功率多模抽运方式设计和实验研究了全光纤化两级放大器。分析了放大器的各种性能参数;1550 nm连续光放大得到最大斜率效率为29%,最大输出功率1.52 W,功率稳定度0.4%;2 kHz脉冲放大时得到最大输出功率1.1 W,功率稳定度0.45%,最大斜率效率25%。并从放大后光谱和时域波形分析了导致脉冲放大时斜率效率和功率转换效率较低的主要原因为Yb3(?)离子波段放大自发辐射(ASE)的出现和Er离子波段ASE的过多积累。在高功率放大时,增益随输入信号功率增大迅速下降;同时结合抽运光频谱随驱动电流变化分析了其对放大器性能的影响。

不同泵浦方式下Er^(3+)/Yb^(3+)共掺光纤放大器的自发辐射谱

用改进的MCVD法和湿法掺杂技术设计制作了2种不同Er3+、Yb3+浓度比的Er3+/Yb3+共掺光纤(EYDF),利用980 nm和1 480 nm泵浦LD对Er3+/Yb3+共掺光纤放大器(EYDFA)的放大自发辐射(ASE)谱进行了研究。利用980 nm LD泵浦时,这2种光纤在C波段的ASE强度都很弱,吸收系数小的EYDF在C波段的荧光强度比吸收系数大的光纤大2个量级。用1 480 nm LD对吸收系数大的EYDF进行泵浦,优化光纤长度,此时C波段荧光强度比用980 nm泵浦时大5个量级。这是由于对于EYDF在976 nm附近Yb3+有很强的非饱和吸收,导致能量传输效率差,因此980 nm LD不适合做高浓度EYDFA的泵浦源。而1 480 nm泵浦时,Yb3+不再作为敏化剂而只起到克服成对Er3+间的浓度淬灭问题,同时起到提高Er3+在石英基光纤中的溶解度的作用。

OPCI系统不同掺杂截面EYDFA增益瞬态的比较

为了研究分组与线路集成系统中突发模式大功率Er/Yb共掺光纤放大器(EYDFA)的瞬态性能,在函数极限的基础上采用迭代算法,建立了基于非线性方程速率方程的、不同掺杂截面EYDFA增益瞬态的比较模型,分析比较了有/无反馈条件下,不同掺杂截面的光分组(OPS)和光线路交换(OCS)输出信号的增益瞬态。结果表明,无反馈条件下,纤芯直径为4.6μm的EYDFA,其OPS和OCS输出信号功率漂移小于纤芯直径为3.6μm的EYDFA,功率漂移的改善约为12%;带反馈条件下,增大掺杂光纤直径,弛豫振荡导致的EYDFA增益抖动随之减小。故增大掺杂光纤直径,能有效抑制EYDFA反馈环路的弛豫振荡。

泵浦功率变化对EYDFA自动增益控制影响的研究

针对EYDFA速率方程的非线性,提出一种迭代求解算法模型。基于环形腔反馈控制方案,采用该算法模型,分析了波分复用条件下,不同泵浦功率对EYDFA增益控制的影响。结果表明:随着泵浦功率的增加,信号增益的可控范围逐渐增大;当多个信道撤除时,随着泵浦功率的增加,增益漂移的峰值也逐渐增大。