侧面泵浦高功率双包层光纤激光器的表面弧形金属槽结构的制作和分析

侧面耦合高功率泵浦光技术是获得高功率稀土光纤激光器的关键技术之一。介绍了一种用于侧面泵浦高功率双包层光纤激光器的表面弧形金属槽结构的制作工艺,并且针对已经实验制作出来的表面连续弧形金属凹槽的侧面耦合结构进行了严格的矢量电磁场理论计算,将120°弧形凹槽等效近似为多层等高不等宽的矩形槽并运用透射矩阵算法对这种近似后的多层矩形结构进行优化设计。这种结构可以用于大功率激光二极管阵列的侧面泵浦中,尤其可用于条形半导体激光器侧面泵浦双包层掺杂光纤,以制作各种大功率稀土光纤激光器。     

多点侧面泵浦双包层光纤激光器的对称夹层结构

 利用基于亚波长衍射光栅理论的介质-金属-介质的对称夹层结构,对掺杂的双包层光纤进行多点泵浦，根据严格的电磁场衍射理论和光栅方程，分析了多点泵浦时，这种耦合结构的泵浦光泄露的问题，证明了多点泵浦时泵浦光的泄露率仅为15.52%，而对信号光则不存在泄露。这种对称夹层结构可以用于多个大功率激光二极管阵列的多点侧面泵浦双包层掺杂光纤中，以制作各种大功率(数kW级)稀土光纤激光器，其最大耦合效率可以达到80%以上。     

掺镱全光纤激光器研究

依据速率方程和边界条件,对高功率多点抽运全光纤激光器进行了研究.通过自制的级联侧面泵浦耦合器搭建全光纤激光器,级联耦合器的单点泵浦效率为96%,泵浦传输损耗为10%,信号光损耗分别是0.18dB和0.87dB;线性谐振腔结构中:前向抽运的光-光转换效率为69%,低于后向抽运中70%的光-光转换效率,与理论分析一致;双向泵浦方式中,在单臂输入975nm泵浦功率为110 W的条件下,激光功率输出为311 W,中心波长为1 080nm,光谱宽度为1.6nm,光-光转换效率为70%,光束质量约为1.3.激光器性能稳定,若增加单臂泵浦功率或级联泵浦耦合器个数,可获得更高功率的激光输出.     

熔融侧面泵浦耦合器光纤夹角对耦合效率的影响

泵浦耦合器是高功率光纤激光器的关键无源光器件,其制作工艺是采用泵浦光纤和主光纤侧面熔融的方法,该方法可以保持主光纤中信号光的低插入损耗,但泵浦光纤和主光纤之间的夹角对耦合效率影响较大。为解决这一问题,根据熔融侧面泵浦耦合器的结构特点,建立了物理模型,推导出各光纤中光功率与夹角关系的方程组,进行了数值仿真和实验论证,结果是随着泵浦光纤和主光纤之间夹角的减小,耦合效率会逐渐增大,但存在临界值,NA值小的泵浦光纤耦合效率高且临界角大,NA为0.22的泵浦光纤,夹角小于9.7时耦合效率最大值为96.9%,NA为0.15的泵浦光纤,夹角小于11.5时耦合效率最大值为97.8%。     

运用泵浦耦合器和飞秒刻蚀光栅制作的全光纤化掺铥光纤激光器(英文)

全光纤化掺铥光纤激光器作为光学参量振荡器的泵浦源,可以实现3～5μm激光输出,在激光雷达和光电对抗领域有着极为重要的应用前景.本文运用全国产化的泵浦光耦合器和双包层掺铥光纤实现了全光纤化掺铥光纤激光器.该光纤激光器采用自制的光纤布喇格光栅作为反射腔镜,增益光纤采用水冷的方式.光纤布喇格光栅通过45fs、800nm的飞秒脉冲光和相位掩模板直接在双包层掺铥光纤上刻蚀得到,泵浦光通过泵浦光耦合器的一端耦合进入增益光纤,产生的激光由泵浦光耦合器的另一端输出.输出激光的最高功率达到22.2W,激光波长为1.96μm,斜率效率约为37%,激光线宽为72.4pm.     

高功率千瓦级(N+1)×1光纤级联泵浦耦合器

分析了泵浦光纤不同锥区长度对(1+1)×1耦合器效率的影响,相同锥区长度不同泵浦臂数量对(1+1)×1耦合器与(2+1)×1耦合器效率的影响,结果表明泵浦光纤锥型区域越长,通过泵浦光纤进入信号光纤的泵浦光越多,泵浦耦合器的耦合效率越高和相同锥区长度下,泵浦臂数量越多,泵浦耦合器耦合效率越低.根据分析结果制作了(1+1)×1耦合器与(2+1)×1耦合器,通过两个(N+1)×1耦合器级联方式形成级联泵浦耦合器.测试了由两个(1+1)×1耦合器组成的级联泵浦耦合器,在总注入泵浦功率602W的情况下输出泵浦功率564W,级联泵浦耦合效率高达93.6%.由两个(2+1)×1耦合器组成的级联泵浦耦合器,在总注入泵浦功率1 210 W的情况下输出泵浦功率1 120 W,级联泵浦耦合效率高达92.5%,实现了千瓦级泵浦功率输出,且两种级联泵浦耦合器信号光损耗均小于0.4%.利用此方法将耦合器形成级联结构可有效提高光纤激光器系统泵浦输出能力,实现千瓦级高功率输出.     

300 W侧面分布式抽运掺Yb全光纤放大器

采用角度磨抛的方式, 在纤芯/包层为20/400 μm双包层掺Yb光纤上制作了侧面抽运耦合器. 该耦合器对975 nm的半导体二极管抽运光的耦合效率最高可达97%, 对1080 nm信号光的泄漏比小于2%. 分析了侧面抽运耦合器的性能以及多个侧面抽运耦合器的级联分布对抽运耦合效率的影响; 同时, 在前向抽运和双向抽运方式下, 分析了级联耦合器的分布及信号光泄漏比对激光器整体效率的影响, 并进行了数值模拟. 采用自行研制的侧面抽运耦合器, 搭建了侧面耦合分布式抽运、掺Yb双包层全光纤主振荡功率放大器, 获得了波长为1080 nm、功率为303 W 的基模激光输出. 进一步增加抽运点个数, 提高抽运功率, 可获得更高的输出功率.     

915nm泵浦混合掺铒/铒镱共掺双包层光纤放大器

研究了一种混合掺铒/铒镱共掺光纤放大器,用掺铒光纤放大器作为输入信号的预放大器,用铒镱共掺双包层光纤放大器作为主放大器。掺铒光纤放大器采用20m长掺铒光纤作为增益介质,采用最大输出功率318mW的单模半导体激光器二极管作为泵浦源,预放大器获得的最大输出功率是113mW。铒镱共掺光纤放大器采用14m长铒镱共掺双包层光纤作为增益介质,采用2个915nm多模半导体激光二极管作为泵浦源,在输入信号功率为10mW、信号波长1555nm时,混合光纤放大器获得了最大输出功率为32.04dBm,即1.6W,与此相应的混合光纤放大器的光-光转换效率为18.5%。     

基于MOPA结构的1120nm掺Yb光纤放大器

基于主振荡功率放大器,采用1120nm光纤激光器作为种子激光,将其注入20m大模场面积单模双包层掺Yb光纤放大器,并用976nm半导体激光器泵浦实现了1 120nm信号光输出.实验中将注入种子激光功率预设为10mW,当半导体激光器泵浦功率增大至1.5 W时,放大器系统开始输出1 120nm信号光.当泵浦功率低于3.4W时,信号光功率随泵浦功率缓慢增长,系统斜率效率较低;而当泵浦功率高于3.4W时,信号光功率随泵浦功率线性增长,斜率效率明显增大,达到48.5%.限于最大注入泵浦功率为6.8W,放大器输出最高1 120nm信号光功率为1.97W,总的光-光转化效率为29%.输出信号光中心波长为1 120.89nm,线宽为0.02nm,极好地保持了种子激光的特性.结合实验情况,利用双包层光纤放大器的稳态理论模型,采用有限差分方法模拟了放大器输出信号光功率随泵浦光功率的变化曲线,结果显示理论模拟所得变化趋势与实验结果吻合良好,系统将在泵浦功率达到200W左右时达到饱和状态,说明目前光纤放大器系统具有很大的功率提升空间.     

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。     

双包层稀土掺杂光纤抽运吸收特性的分析

建立了复折射率纤芯结合有限差分束传播法的双包 层稀土掺杂光纤抽运吸收效率数值模型,利用该模型对几种常 用内包层外边界结构下双包层稀土掺杂光纤的抽运吸收系数进 行了详细的分析,得出相应双包层光纤的抽运吸收特性. 分析结果对双包层稀土掺杂光纤的优化设计具有重要的指导意义.     

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.     

10-W cladding-pumped fiber laser with single transverse mode output

A Yb-doped double-clad fiber laser is demonstrated with a measured power output of 10.6 W and a fundamental spatial mode. The optical-to-optical conversion efficiency is 44% and the slope efficiency is 86% closed to quantum efficiency of optical conversion. In our laser system, a D-shape (340 μm/400 μm) inner cladding Yb-doped fiber is used as the gain material within the Fabry-Perot cavity. Multimode diode pump radiation is injected into the cladding through an end facet of the composite fiber.     

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%。     

High-power Yb-doped multicore ribbon fiber laser

A highly elongated double-clad ribbon fiber that comprises a pure-silica inner cladding with transverse dimensions of approximately 1.4 mm by 0.23 mm with a linear array of ten ytterbium-doped cores has been fabricated and operated in a simple laser configuration pumped by two diode stacks. The fiber laser yielded 320 W of output power at a center wavelength of 1045 nm in a combined beam with beam propagation factors of approximately 2 (perpendicular to the array) and approximately 150 (parallel to the array) for 576 W of launched pump power. The slope efficiency with respect to absorbed pump power was 62%. The prospects for further power scaling and improved beam quality and efficiency are discussed.     

Light propagation in the multi-mode double-clad erbium: ytterbium co-doped fiber: theory and experiment

The pump light and forward- and backward-amplified spontaneous emissions (ASE±) propagation in the multi-mode double-clad erbium: ytterbium co-doped fiber are analyzed numerically and measured experimentally. And the light propagation in hexagonal inner cladding based on geometrical optics are analyzed comprehensibly. We obtained that the suitable length of the fiber in optical fiber lasers is 2–2.5 m, and the 2 m long fiber emits at 1535 and 1543 nm simultaneously, and the peak-value wavelength of ASE+ changes to the long wavelength with an increase in the pump power.     

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.     

Fabrication and characteristics of silica optical fiber doped with InP nano-semiconductor material

We fabricated a novel special silica optical fiber doped with nano-semiconductor material InP in double cladding layers by using conventional modified chemical vapor deposition (MCVD) process. During the deposition process, InP powder was placed at the entrance of silica substrate tube and vaporized by high temperature. With the help of nitrogen gas flow, the vaporized InP was carried into silica substrate tube and deposited on the inner surface in the form of nano-particle. The physical structure and amplification characteristics of the special fiber were investigated. From the refractive index distribution of the preform, we can observe obvious increase in inner cladding index, which attributes to InP dopant. By using 532 nm LD as pump, a broadband amplified spontaneous emission (ASE) was demonstrated in the wavelength range from 1,080 to 1,350 nm. The proposed nano- semiconductor doped fiber with optical amplification is expected to a wide application in optical fiber communications.     

Off-axis pumping of a photonic crystal fiber laser

We present a new method for free space pumping of double-clad photonic crystal fiber lasers and amplifiers. The method is based on off-axis injection of the pump beam, exploiting the relatively high numerical aperture of the photonic crystal fiber cladding. It prevents feedback from the laser into the pump source, does not require any special treatment to the fiber, and could lead to a more compact resonator. Experimental results with the new pumping method show improved laser performance.     

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。