空气包层大模场面积掺镱光子晶体光纤研究

采用改进的化学气相沉积法和气相液相混合掺杂技术制备大芯径掺镱石英光纤预制棒, 以此作为有源纤芯制备了纤芯直径约90 μm的掺镱双包层光子晶体光纤, 纤芯组分为镱铝磷共掺.双包层光子晶体光纤的模场面积约1330 μm², 纤芯数值孔径0.065,包层数值孔径0.5.首次实现了国产掺镱光子晶体光纤的高功率高效率激光输出, 1 m长的光子晶体光纤激光器实现102 W 激光输出,斜率效率76%.     

Demonstration of fundamental mode only propagation in highly multimode fibre for high power EDFAs

The use of short lengths of large core phosphate glass fibre, doped with high concentrations of Er or Er:Yb represents an attractive route to achieving high power erbium doped fibre amplifiers (EDFAs) and lasers (EDFLs). With the aim of investigating the potential of achieving diffraction limited output from such large core fibres, we present experimental results of fundamental mode propagation through a 20 cm length of passive 300 μm core multimode fibre when the input is a well-aligned Gaussian beam. Through careful control of fibre geometry, input beam parameters and alignment, we measured an output M² of 1.1 ± 0.05. The fibre had a numerical aperture of 0.389, implying a V number of 236.8. To our knowledge, this is the largest core fibre through which diffraction limited fundamental mode propagation has been demonstrated. Although the results presented here relate to undoped fibre, they do provide the practical basis for a new generation of EDFAs and EDFLs.     

后腔镜对掺Yb3+双包层光纤激光器性能影响的研究

采用自行研制的内包层为矩形的掺Yb^3 双包层石英光纤，以透射率不同的一组二向色镜为后腔镜构成了双包层光纤激光器。实验证明：后腔镜具有较高透射率为佳；后腔镜可以实现对激光波长的控制；激光斜率效率与后腔镜透射率之间的关系符合指数变化规律，在本实验的条件下，斜率效率的最大值约60％。     

矩形内包层掺Yb3+石英光纤的研制及其抽运性能

利用改进的化学汽相沉积工艺加溶液掺杂法,配合光学加工技术,自行设计并研制出内包层为矩形等新颖结构的掺Yb^3 双层石英光纤,实现了上述光纤的包层抽运激光器的成功运转,矩形光纤在1075．6nm波长处获得84mW的最大激光输出功率,斜率效率达77％。     

双包层掺Yb3+光纤激光器的关键技术

大功率光纤激光器作为第三代激光器的代表,在激光加工和激光武器方面有着重要应用.介绍了掺Yb3+光纤激光器的发展历程,理论上分析了光纤激光器的泵浦阈值和输出功率,讨论了实验过程中涉及到的大功率LD泵浦、光纤耦合和双包层光纤等关键技术,为同类激光器的改进设计和深入研究提供参考.     

包层泵浦的L波段Er3+/Yb3+共掺光纤激光器

报道了一种工作波长在L波段的包层泵浦Er³⁺/Yb³⁺共掺光纤环形激光器. 环形腔内的激光工作介质为一段9 m长的Er³⁺/Yb³⁺共掺高掺杂光纤. 利用6个976 nm LD同时抽运前段Er³⁺/Yb³⁺共掺双包层光纤产生的放大自发辐射谱作二次抽运源, 使腔内增义谱由C波段移到L波段, 实现了L波段光纤激光器的稳定输出; 采用包层泵浦技术, 在抽运功率为3594.5 mW时, 测得泵浦入纤功率为2731.8 mW, 实现了输出连续功率最大518.4 mW,斜率效率达到19% 的激光输出; 所形成激光的工作波长为1613.94 nm, 激光光谱的3 dB带宽为1.5 nm, 边模抑制比接近于50 dB.     

双端抽运的掺Yb^3＋双包层光纤激光器中合作发光效应

合作发光效应、热效应以及非线性效应限制了单根掺Yb^3＋光纤激光器输出功率的进一步提高。根据能级间的吸收与辐射，分析了掺Yb^3＋双包层光纤中的合作发光效应，分析表明，随着Yb^3＋的掺杂浓度的增大，光纤中合作发光增强，抽运光越强，合作发光也越强。实验研究了输出功率61．6W，斜率效率为55％的双端抽运的掺Yb^3＋双包层光纤激光器的合作发光效应，研究表明，随着抽运光功率的增大，合作发光强度增强，掺杂浓度越大，光纤中合作发光效应也越强。这一结果有利于进一步提高掺Yb^3＋光纤激光器的效率。     

大模场掺镱双包层光子晶体光纤内包层新型结构研究

制备了掺镱多组分硅酸盐光子晶体光纤纤芯材料。其折射率为1.586,有效荧光半高宽为85.3 nm,荧光寿命为1.30 ms。分析了光纤结构参数对光子晶体光纤的归一化频率（单模截止条件）、数值孔径、有效模面积、非线性效应和限制损耗等参数的影响。设计了以该材料为纤芯,内包层为八边形、五层空气孔的新型结构光子晶体光纤。用有限元法对该光子晶体光纤性能进行了数值模拟。结果表明,该光纤有效模场面积为1 150 μm²;当空气孔直径为21.6 μm、孔间距为60 μm时,内包层数值孔径达到0.45。     

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     

Inner cladding influence on mode interaction in symmetry-free photonic crystal fibers under heat load

A further output power scaling of Yb-doped double-cladding photonic crystal fiber lasers, required for practical applications in many industrial fields, is currently prevented by thermal effects, which significantly worsen the beam quality. In this work the mode interaction and, consequently, the single-mode regime of Yb-doped air-silica symmetry-free photonic crystal fibers have been numerically investigated in different heat load conditions using simulation tools based on the finite element method. The effect of the main inner cladding geometric parameters, in particular of the inner cladding dimension, on the guided-mode delocalization has been analyzed, with the aim to identify a design of the large mode area active fiber providing single-mode operation despite the presence of thermal effects. Simulation results have demonstrated that the inner cladding enlargement causes a stronger coupling between core-guided and cladding modes, as well as an increase of the differential overlap between fundamental and first higher-order mode for moderate heat load values. However, the inner cladding influence becomes less important under severe heat load, being the fiber behaviour mainly affected by the thermally-induced refractive index change in the doped core.     

掺Yb3+双包层光纤激光器的数值分析

 对掺Yb³⁺双包层光纤激光器不同参数情况下的输出功率和增益分布进行了数值模拟，分析了一端泵浦和双端泵浦方式下输出特性的差异，激光沿光纤长度方向的分布，输出功率与光纤长度、腔镜反射率及泵浦功率的关系。结果显示：两端泵浦较一端泵浦增益更加平坦，输出功率也稍高；当泵浦光波长为975nm时，输出激光功率对光纤长度更为敏感，最佳光纤长度相对于泵浦光波长为915nm时短且转化效率高；在大功率长光纤的情况下，光纤有损耗时输出功率随输出腔镜反射率的增加单调地减小，无损耗时输出功率不随输出腔镜反射率变化。     

Design of zero dispersive double clad fiber for high efficiency operation of two color light

A double clad solid silica fiber is newly designed for applications which need the high efficiency operation of two colors of light. Ultrashort pulses with a central wavelength of 800?nm are delivered by the core of the double clad fiber which can realize the transmission of the optical pulses with a net chromatic dispersion of zero. This is achieved by integrating the double clad fiber with a pair of long period gratings, which allows optical pulses to propagate in a higher order mode (LP₀₂) in the middle of the fiber as well as in a fundamental mode (LP₀₁) at the beginning and end of the fiber. The index profile of the double clad fiber is engineered so that the higher order mode has high anomalous dispersion that can be used to compensate for normal dispersion of the fundamental mode. By controlling the lengths of the fiber where pulses are in a fundamental and in a higher order modes, the fiber with total zero dispersion can be realized. The double clad fiber can collect 100?% of visible light within the numerical aperture of 0.21 with a loss of the optical pulses less than 1?%. The design of this fiber is essential for applications including fiber-optic nonlinear imaging for compactness, robustness, and low optical power loss in dispersion compensation.     

Investigation of various transmission properties and launching techniques of plastic optical fibres suitable for transmission of high optical powers

The significant parameters for plastic fibres with various core/cladding combinations are given: refractive index, numerical aperture, critical angle of total internal reflection at the core/cladding interface and maximum angle of aperture. The output power of a plastic fibre (PS/PMMA) was measured as a function of the angle of incidence. The results are interpreted using the ray optical fibre transmission model. Various launch-loss-reducing optical end-face working procedures are compared. We also investigated a method to avoid Fresnel reflection losses by a Brewster angled fibre input end-face for a linearly polarized light beam. The transverse and longitudinal intensity distribution of the output beam of a PS/PMMA fibre was measured. We conclude that a single large core clad plastic fibre is a promising alternative to a multi-glass fibre bundle for some applications.     

国产掺镱双包层光纤的激光特性

 采用MCVD方法研发了掺镱双包层光纤，并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400/450μm，数值孔径为0.36,纤芯直径约为16μm，数值孔径约为0.18。荧光谱线的范围为1 000~1 140 nm，1 030 nm处的峰宽大于50 nm。采用大功率激光二极管单端泵浦6 m长的双包层光纤，在泵浦入纤功率为61 W时， 获得了32 W的激光输出，斜率效率为64%。该光纤在高功率处未发现饱和现象，通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率激光器件。     

Experimental Investigation of High Power Erbium-Ytterbium Co-doped Double Clad Fibre Laser

All-fibre high power erbium-ytterbium co-doped double clad fibre lasers are proposed and demonstrated. By using different back-cavity mirrors, the different double clad fibre lasers are constructed. It is experimentally found that the output behaviour of laser can be controlled by a back-cavity mirror. The lower the reflectivity of the back-cavity mirror, the higher the output power and the high the slop efficiency. The maximum output power is about 1.6 W and the slop efficiency is 27.6%.     

包层泵浦技术在光纤通信中的应用

包层泵浦技术以其独特、高效的特点越来越引起人们的关注，有希望能推动光纤通信新的发展。本文详细介绍了包层泵浦技术在光纤通信中的应用，包括包层泵浦光纤放大器、包层泵浦光纤激光器以及作为光纤拉曼放大器、激光器泵源的大功率掺镱双包层激光器。并且展望了包层泵浦技术中一些关键技术的发展方向。     

Investigation on characteristics of W-type fiber with an inner cladding made of negative refractive index materials

A doubly clad optical fiber with an inner cladding made of negative refractive index material was proposed and the modes distribution, dispersion and time delay were investigated by fully vectorial numerical method. The results indicate that HE₁₂ mode can be operated as a single mode, the cut-off frequency of modes shifts to low normalized frequency with increasing thickness of inner cladding made of negative index materials, large negative dispersion and time delay can be obtained and tailored by the inner cladding. These results provide theoretical basis for designing novel fibers or optical devices.     

窄线宽掺Yb3+双包层光纤激光器研究

 与通常的双包层光纤激光器不同，光纤前端面与二色镜拉开一个小的距离，构成了Fabry-Perot滤波器。理论分析了Fabry-Perot滤波器效应。通过调节光纤前端面与二色镜之间的距离，实现了掺Yb³⁺双包层光纤激光器的窄线宽激光输出，中心波长为1 082.79 nm，谱线宽度为0.14 nm，斜率效率为20%，最大输出功率为0.62 W。     

熔锥型侧面泵浦耦合器的研究

 现在高功率光纤激光器和光纤放大器采用的双包层掺杂光纤,相对于从半导体泵浦激光器发射出的多模泵浦光束的大发散角,其内包层的直径很小,因此把泵浦光有效地耦合到双包层掺杂光纤的内包层是一个急需解决的难题。研制一种熔锥型侧面泵浦耦合器,可以大幅度提高泵浦光功率,实现增益光纤的多点泵浦,在双包层光纤放大器中使用良好,安全稳定,实现了较高的耦合效率,达到了70%,信号光通过率98%,信号输入与泵浦输入的隔离度大于50 dB,泵浦输入对输出端反向传输光的隔离度27 dB。通过对比结构紧凑性、耦合效率、系统稳定性等相关指标发现,熔锥型侧面泵浦耦合器完全可以满足高功率光纤激光器和光纤放大器的使用要求。     

Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser

A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 < 1.4 for 92.6 W launched pump power from a diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.