Experimental demonstration of novel end-pumping method for double-clad fiber devices

We present experimental demonstration of an end-pumping scheme based on splicing the multimode pump and single-mode signal fibers directly to a double-clad fiber with a tailored cross section. The method is used to pump a double-clad, erbium- and ytterbium-doped, fiber ring laser. The efficiency of the end-pumping method is tested by determining the slope efficiencies of the fiber ring laser and the fiber laser in a Fabry-Perot configuration. Comparable slope efficiencies are found when both laser configurations have similar output coupler ratios. The developed pumping scheme and double-clad fiber can find applications in cost-effective power fiber amplifiers and lasers.     

侧面抽运的掺Yb双包层光纤激光器

利用光纤角度磨抛侧面耦合新技术研究了侧面抽运的掺Yb双包层光纤激光器。实验上采取新的加工工艺获得了端面具有小锐角磨抛斜角的多模光纤,专门设计的高精密机械调整结构有效地将多模光纤的斜面和双包层光纤的侧面精确对准,通过不同的折射率匹配材料进行的研究,发现折射率匹配材料对于注入功率和抽运效率都有较大影响。实验中通过光纤角度侧面耦合器能够注入1．12W抽运光进入双包层光纤,侧面耦合效率最高可达80％。将该侧面耦合技术用于侧面抽运的掺Yb双包层光纤激光器,在单个尾纤输出的半导体激光器侧面抽运下得到光纤激光器的最大连续激光输出功率282mW,斜率效率为55．5％。实验结果表明,光纤角度磨抛耦合技术是掺Yb双包层光纤激光器的一种简单有效的侧面抽运方式。     

Multi-coupler side-pumped Yb-doped double-clad fiber laser

The side-coupler of angle polished method, using angle-polished multimode fiber and optical adhesive, is used to efficiently pump an Yb-doped double-clad fiber laser. The maximum coupling efficiency of 78.6% is achieved by the side-coupler for a multimode fiber with a circular core of 200 μm and a double-clad fiber with a 350/400 μm D-shaped inner cladding. While laser diodes (LDs) with three side-couplers are simultaneously used as pump sources, maximum output power of 1.38 W and slope efficiency of 48.9% are demonstrated in the fiber laser system.     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法 ,在D形内包层掺Yb3 双包层光纤一端直接写制出Bragg光栅 ,用作双包层光纤激光器的输出腔镜 .试验得到了线宽为 0 196nm ,波长为 10 5 8 2nm ,最高输出功率为 5 70mW的稳定激光输出 ,解决了激光器中模式竞争造成的输出不稳定现象 .从速率方程出发 ,对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析 ,结果与实验符合很好     

双包层光纤光栅选频双包层光纤激光器

双包层光纤激光器中多采用法布里珀罗(F-P)线形腔结构,谐振腔为一只二向色镜和光纤端面菲涅耳反射镜(反射率约为4％)构成,这属于一种有缺陷的腔结构,其稳定性不好,产生激光的波长很难得到有效控制,后腔镜不能精确选择激光器的输出波长,激光器的输出谱线较宽。在某些对激光波长有明确要求的应用中,该结构会受到限制。采用布拉格光纤光栅作腔镜,利用其窄带滤波特性,可以得到窄线宽的激光输出,目前报道的作为腔镜的布拉格光纤光栅为在单包层光敏光纤上制作而成,然后分别将不同反射率的光纤光栅与双包层增益光纤熔接,这给腔镜与双包层光纤之间带来很大的耦合损耗,影响了激光器的功率输出。该文报道了用相位掩模法在双包层光纤芯上写入了布拉格光纤光栅,并把此光纤光栅做为后腔镜．对长度为10m、20m的D形掺Yb^3 双包层光纤激光器进行实验研究,在1058nm附近得到稳定的窄线宽激光输出,3dB带宽为0．329nm。激光器最大输出功率为570mW。最后对实验结果进行了理论分析。     

Yb3+-doped double-clad fiber laser with all fiber cavity

A novel all fiber cavity Yb3+-doped double-clad fiber laser (DCFL) based on two double-clad fiber (DCF)Bragg grating is presented. The fiber Bragg gratings (FBGs) as the input and output mirrors have been formed in Yb3+-doped DCF with the phase-mask method, and their reflectivities are 99% and 22%,respectively. When the input pump power is 417 mW, the maximum output power is 144 mW with linewidth ＜0.1 nm at the wavelength of 1.057μm, over 40-dB signal-to-noise ratio (SNR), and 50.8% slope efficiency.     

大模场双包层光纤光栅的光谱特性

在分析大模场双包层光纤的模式特性和测试光路中光功率分配的基础上,根据耦合波理论和传输矩阵法,对不同情况下大模场双包层光纤光栅的透射谱和反射谱进行数值分析,结果表明光谱形状取决于模式间的功率分配,通过基模的透射谱可以测量双包层光纤光栅的真实反射率。采用相位掩模法制作了基模反射率不低于99.7%的20/400μm大模场双包层光纤光栅,测试了不同情况下的反射谱和透射谱,实验结果和理论分析的结论一致。     

Numerical analysis of stimulated inelastic scatterings in ytterbium-doped double-clad fiber amplifier with multi-ns-duration and multi-hundred-kW peak-power output

We investigate the stimulated Brillouin scattering (SBS) and the stimulated Raman scattering (SRS) in an ytterbium-doped double-clad fiber amplifier that outputs optical pulses with multi-ns-duration and multi-hundred-kW peak-power. The ytterbium-doped double-clad fiber amplifier is simulated by a model which is composed of a set of propagation-rate equations. The simulated results show that SBS and SRS will deform the output signal pulse in both the time domain and the spectral domain, and degrade the performance of the ytterbium-doped double-clad fiber amplifier seriously. It is shown in our simulation that the troublesome SBS can be effectively suppressed by broadening the signal linewidth to a critical value of 0.07 nm in our calculation, and the effect of SRS can be suppressed using a large-mode-area fiber with proper length. The model and the simulated results are very useful for designing an ultra-high-power ytterbium-doped double-clad fiber amplifier.     

后向泵浦高功率掺镱光纤放大器的非弹性散射效应

 在考虑受激布里渊散射和受激喇曼散射效应的基础上,数值求解了双包层掺镱光纤放大器的速率-传输方程,分析了后向泵浦高功率掺镱光纤放大器在不同信号光线宽、光纤长度和纤芯直径下的输出特性,研究了受激布里渊散射和受激喇曼散射的抑制条件。计算结果表明:在后向泵浦方式下,若掺镱光纤长度小于0.68 m,纤芯直径大于26 μm,信号光线宽大于0.04 nm,则放大过程中的受激布里渊散射和受激喇曼散射能同时得到有效抑制。     

包层泵浦掺镱光纤激光器的理论和实验研究

从包层泵浦光纤激光器的速率方程理论出发,推导出了稳态下包层泵浦光纤激光器的输出功率,斜率效率和阈值功率的解析表达式,进行了数值模拟,对模拟结果进行了简单分析。并进行了实验研究,实验采用中心波长为975nm的激光二级管单端泵浦内包层形状为D型的包层光纤,利用二相色镜和光纤端面反馈构成谐振腔,采用了两套不同的准直耦合系统,得到的最高输出功率为24W,总的光-光转换效率为53.5%。     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法，在D形内包层掺Yb3+双包层光纤一端直接写制出Bragg光栅，用作双包层光纤激光器的输出腔镜.试验得到了线宽为0.196nm，波长为1058.2nm，最高输出功率为570mW的稳定激光输出，解决了激光器中模式竞争造成的输出不稳定现象.从速率方程出发，对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析，结果与实验符合很好. 关键词： 双包层光纤光栅 掺Yb3＋双包层光纤激光器 相位掩模 速率方程     

Flat supercontinuum generation covering C-band to U-band in two-stage Er/Yb co-doped double-clad fiber amplifier

Supercontinuum generation in the gain fiber in two-stage nanosecond pulse Er/Yb co-doped double-clad fiber amplifier had been demonstrated for the first time to our knowledge instead of the conventional method in which nonlinear fiber was pumped by lasers. The Er/Yb co-doped double-clad fiber acts as the gain media and nonlinear media. This route reduces the splice between fiber laser and nonlinear fiber. The supercontinuum was achieved with spectrum range from 1530 nm to beyond 1700 nm at 6 W output power covering the total C-band to U-band. From the analyzing of the spectra at different stages in the amplifiers, it can be found that it is the modulation instability in the anomalous dispersion regime that initiates the supercontinuum gereration.     

高功率双包层光纤激光器

介绍了高功率双包层光纤激光器的结构和工作原理，综述这种新型光纤激光器的主要特点及其在国内外的最新进展状况，展望了双包层光纤激光器的应用前景。     

Threshold characteristics of linear cavity Yb-doped double-clad fiber laser

The threshold characteristics of linear cavity Yb³⁺-doped double-clad fiber laser have been studied theoretically and experimentally. By solving rate equations, the expression for threshold pump power is obtained. The effects of fiber length, mirror reflectivity, pump wavelength, laser wavelength and Yb³⁺ concentration on threshold pump power are discussed. Then, the Yb³⁺-doped double-clad fiber laser with linear cavity is developed. By using various output couplers, threshold pump power has been measured. The experimental results are in accord with theory.     

Diode-pumped 1018-nm ytterbium-doped double-clad fiber laser

We report a 1 018-nm ytterbium-doped double-clad fiber laser pumped by 970-nm diode. A pair of fiber Bragg gratings with reflectivities of 99.9% and 9% at a center wavelength of 1 018.9 nm are employed as cavity mirrors. The ytterbium-doped double-clad fiber is a 2.6-m-long Liekki fiber. Laser output power of 7.5 W at 1 018 nm is obtained under the pump power of 59.2 W. The overall slope efficiency of the fiber laser is about 16%. This low slope efficiency is mainly due to the incomplete absorption of the pump power.     

利用光纤光栅的高功率掺镱光纤激光器

报道了利用一对光纤光栅作为双包层Yb^3 掺杂光纤激光器的谐振腔，激光二极管光纤模块(LD)进行了抽运，并采用锥形光纤实现了全光纤化结构，获得了高功率双包层光纤激光器。光纤光栅通常是用融接技术实现与双包层光纤的一体化连接的，采用的双包层光纤为内包层为梅花瓣形结构的掺Yb^3 离子的石英光纤，采用的抽运源为中心波长为970nm的半导体激光光纤输出模块，在抽运源电流达到2．4A时，获得了10．8W的光纤激光器单横模输出，输出波长1100．5nm，峰值半峰全宽(FWHM)为0．54nm，激光器斜效率为59％。     

掺Yb3+双包层光纤激光器的实验研究

采用自行研制的掺Yb³⁺双包层石英光纤和包层泵浦技术,对不同光纤长度的双包层光纤激光器的输出特性进行了实验研究.对实验中的最佳吸收长度问题做了分析,并讨论了引起激光波长随长度变化的原因.     

Side pumping of double-clad photonic crystal fibers

Side pumping of double-clad photonic crystal fibers is experimentally demonstrated. Optical access to the multimode cladding is obtained by collapsing the airholes over a short length of fiber while leaving the inner single-mode core undisturbed. Coupling efficiencies greater than 90% are obtained. A side-pumped Yb fiber laser with a slope efficiency of 81% is demonstrated with this method.     

Fabrication and Lasing Property of YbYb3+-doped Double-Clad Fibers with Novel Inner Cladding

The Yb3+-doped double-clad fibers with novel inner cladding have been made by using MCVD process, solution-doping method and optical machining together. The laser power and slope efficiency of the fiber lasers are higher than 1.8W and 50% respectively.     

高功率双包层光纤激光器抽运技术的方案分析

介绍了高功率光纤放大器双包层光纤的结构特点和双包层抽运的基本原理,在此基础上对高功率双包层光纤激光器的抽运关键技术作了分析,详细讨论了端面抽运技术、熔锥侧面抽运技术、内嵌反射镜抽运技术、角度抛光侧面抽运技术和V形槽侧面抽运技术等多种侧面抽运技术的结构及系统性能参数,并对各种侧面抽运技术的优缺点作了比较分析.研究结果表明,侧面抽运比端面抽运更有利于获得高功率激光输出,而在侧面抽运技术中则以V形槽侧面抽运技术为佳.