微透镜光纤在半导体激光器中的应用研究

对几种典型的半导体激光器与光纤的耦合特性进行分析,提出提高耦合效率所采用的微透镜光纤的结构.介绍熔拉型、化学蚀刻型、研磨抛光型、切削型、自聚焦光纤型和铸模型等微透镜光纤的制作原理和工艺以及目前达到的指标,并对各种形式的透镜光纤进行了评价.提出了提高耦合效率和失调容差、降低插损的新思路.     

A new lensed-fiber configuration employing cascaded GI-fiber chips

A new scheme is proposed for lensed fibers having high coupling efficiency between laser diodes and single-mode fibers with a long working distance. The new lensed fiber consists of a pair of GI-fiber tips having different focusing parameters. The measured net coupling loss between a laser diode operating at a wavelength of 1.3 μm and a single-mode fiber is as low as 1.5 dB. The working distances are around 50 μm, much longer than those of conventional lensed fibers     

提高大功率激光器与光纤耦合效率的新型光腔

提出并实现了一种新型多有源区隧道级联大光腔半导体激光器,增大了半导体激光器激射窗口的高度,得到低于20°的垂直发散角,从而显著提高了激光器与光纤的耦合效率。将其与多种形式和规格的透镜光纤进行测试,耦合效率可以提高30%以上。     

A lensed-fiber coupling scheme utilizing a graded-index fiber and ahemispherically ended coreless fiber tip

A new configuration of lensed fibers as the coupling between laser diodes and single-mode fibers is proposed. The lensed fiber consists of a hemispherically ended coreless-fiber and a quarter-pitch length of a graded-index fiber. Fabrication is quite simple and rapid. Basic characteristics of the new configuration, including long working distances and wide tolerances, are experimentally verified. The new configuration is suitable for integration-oriented coupling between arrayed laser diodes and an array of single-mode fibers     

平端光纤与锥端微透镜光纤的耦合研究

建立了平端光纤与锥端微透镜光纤对耦合的理论模型,得到耦合系数的计算公式.用研磨技术制作了几种不同锥角的光纤,并对它们进行耦合试验,得到最大耦合效率.实验表明实验结果与理论计算结果是一致的.     

锥形微透镜保偏光纤与超辐射发光二极管的耦合

对采用锥形光纤微透镜的保偏光纤与超辐射发光二极管的耦合进行了理论分析.制作出几种不同的微透镜保偏光纤,并对它们进行了耦合试验,找到了制作具有高耦合效率的微透镜保偏光纤的方法.     

SLED中熔锥形透镜光纤耦合设计

文章提出一种熔锥形透镜光纤的设计方法,与常用的圆锥形保偏单模光纤相比,熔锥形透镜光纤与超辐射发光二极管(SLED)管芯的耦合效率可由原来的45%提高到60%,工作距离由7 μm达到超过15 μm,且前者的耦合容差远远大于后者.对于新设计的熔锥形透镜光纤,文章还给出了偏移和偏心与耦合效率的关系曲线图.     

A new scheme of conical-wedge-shaped fiber endface for coupling between high-power laser diodes and single-mode fibers

A new scheme for the lensed fiber employing a conical-wedge-shaped fiber endface (CWSFE) for coupling between the high-powered 980-nm laser diodes and single-mode fibers (SMFs) is proposed. The CWSFE was fabricated by following grinding and polishing techniques and then through heating in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 84% has been demonstrated. The higher coupling efficiency of the CWSFE lensed fiber was attributed to the better matching of both the elliptical Gaussian field distribution and the aspect ratio between the laser source and the fiber. In comparison to other fabrication techniques of lensed fiber used in high-power diode lasers, the advantages of this novel CWSFE structure are the ability to control over two axial curvatures and a small fiber offset through grinding and polishing processes to form a good elliptical endface. The results of this study have led to the development of a simple and reproducible fabrication process for achieving a high-yield and high-coupling CWSFE structure that is suitable for use in commercial high-power pump laser modules.     

Optical Coupling Methods for Cost-Effective Polymer Optical Fiber Communication

In this paper, we report cost-effective light coupling methods for polymer optical fiber (POF) communication. Here, we compare the various optical coupling schemes in detail. By optical simulations, we analyze the conventional light coupling schemes, namely the direct coupling, lens coupling, and lensed fiber coupling. The simulation studies reveal that a lensed fiber tip particularly at the receiver side improves the light coupling efficiency to a great extent. The optimized lensed POF design confers an 85% coupling efficiency. Lensed POFs are realized with two low-cost fabrication methods. The characterization of the lensed POF are carried out to evaluate the lensing properties and hence to optimize the fabrication process.     

A fiber lens with a long working distance for integrated couplingbetween laser diodes and single-mode fibers

A new scheme is proposed for lensed fibers with a long working distance, as used in the coupling between laser diodes and single-mode fibers. The scheme consists of the combination of a hemispherically-ended coreless-fiber tip and an expanded-core fiber. The working distance is measured as 169 μm with a relatively low coupling-loss of 4.2 dB at a wavelength of 1.49 μm. Tolerances for a 1-dB loss increment for axial-, lateral-, and angular-misalignment are 35, 2.6 μm, and 0.8 degrees, respectively. The new configuration is suitable for alignment-free coupling between arrayed laser diodes and an array of single-mode fibers     

Design optimization of wedge-shaped lensed fibers for fiber-laser coupling: Fresnel reflection and non-Gaussian mode effects

Two approaches, i.e., a diffraction model considering Fresnel reflection and a paraxial beam propagation method are utilized to optimize the design of wedge-shaped lensed fibers for coupling between laser diodes of highly asymmetrical beam and single-mode fibers. It is demonstrated for the first time that, in contrast to the prevailing view, the non-Gaussian fiber-mode shape modification by the wedged fiber tip greatly reduces the coupling efficiency when the wedge angle is relatively large, while the Fresnel reflection is found to play an insignificant role. The fundamental cause of the non-Gaussian shape effect is fully explored and, consequently, a novel design is proposed to suppress this effect and increase coupling efficiency. Moreover, the novel design is relatively simple, and it does not complicate the fiber tip fabrication process.     

Solder-assembled high coupling efficiency single-mode laser modules using micro-heaters and precompensation technique

In this paper, we are proposing a hybrid integration platform, on which a single-mode lensed fiber can be actively aligned to a semiconductor laser, and then solder-attached to the platform with the help of on-board thin-film heaters. We have demonstrated 50% coupling efficiency with conically lensed single-mode fibers, bonded with gold-tin (AuSn) eutectic solder. The loss of alignment due to solder solidification has been carefully measured and compensated during the subsequent correctional alignment step taking advantage of the reworkability feature of the solder-joint. Two types of fiber sub-assemblies have been tested: uncoated bare fiber housed within a metallized ceramic ferrule, and nickel/gold coated bare fiber directly solder-bonded to the platform. Statistical data confirms that in both the cases, 95% of the loss of original coupling was restored by the precompensation technique.     

多模与单模光纤级联系统对激光束的传输

分析了激光束在光纤中的非线性传输损耗,理论上证明了受激布里渊散射(SBS)是光纤传输能力的主要限制因素;实验上在532nm波段对长度为5m,纤芯半径为1.75μm,数值孔径(NA)为0.11的单模光纤的传输能力进行了测定,结果与理论一致。采用模场耦合理论,推导出多模光纤与单模光纤的直接耦合效率表达式,计算得到耦合效率与所选用的多模光纤和单模光纤的纤芯芯径之间的模拟关系。激光器输出波长为532nm;多模光纤的数值孔径为0.11,纤芯半径为12.5μm;单模光纤的数值孔径为0.11,纤芯半径为1.75μm,实验结果与理论基本吻合。根据理论和实验结果,设计出多模光纤与单模光纤混合传输方案,在柔性传输较高激光功率的同时可以得到高光束质量。     

YAG激光泵浦光纤产生受激喇曼散射

本文利用YAG激光泵浦光导纤维产生受激喇曼散射,并利用所摄取的受激喇曼光谱图定出斯托克斯线波长,计算样品的喇曼频移,对实验中所观察到的现象进行分析讨论。     

基于液体选择填充光子晶体光纤的波分解复用器研究

设计了一种基于液体选择填充三芯光子晶体光纤的1.31/1.55um波分解复用器。中间为缺失一个空气孔的普通二氧化硅纤芯,左右两纤芯填充了不同折射率的液体材料。根据光纤的消逝场耦合的模式理论,不对称相邻波导存在波长相关耦合。不同填充折射率的两纤芯与中间纤芯分别耦合,构成两个不同响应波长的光滤波器。通过选择合适光纤长度,可实现不同波长光的分离。采用全矢量有限元法分析了光纤的传输特性,讨论了填充不同折射率液体时波导间的模式耦合,得到了其匹配波长与耦合长度。基于光束传播法仿真发现,长度为4.88 mm的光纤能实现1.31/1.55 um波长光的解复用。     

A novel scheme of lensed fiber employing a quadrangular-pyramid-shaped fiber endface for coupling between high-power laser diodes and single-mode fibers

This paper proposes a new scheme for the lensed fiber employing a quadrangular-pyramid-shaped fiber endface (QPSFE) for coupling between the high-power 980-nm laser diodes and the single-mode fibers (SMFs). The QPSFE was fabricated by grinding and polishing techniques and then heating in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 83% has been demonstrated. Based on the far-field profile measurements, the higher coupling efficiency of the QPSFE lensed fiber was attributed to the better matching of both the elliptical Gaussian field distribution and the aspect ratio between the laser source and the fiber lens, The advantage of the QPSFE structure was to be able to control two axial curvatures, and, therefore, this novel QPSFE can form any different aspect ratios of elliptical microlenses to match the far field of the high-power diode lasers as well as the commercial diode lasers used in lightwave communications.     

Practical Design of Lensed Fibers for Semiconductor Laser Packaging Using Laser Welding Technique

We propose a set of guidelines for the practical design of lensed fiber for the optical coupling of semiconductor lasers in butterfly packages using laser welding. These guidelines have optimized the tradeoff between coupling efficiency and alignment tolerance. Moreover, a radius of curvature of 11 $mu$m is shown to be optimal for semiconductor lasers whose divergence angles range from 5$^{circ}$ to 30$^{circ}$. To experimentally evaluate the design, lensed fibers were assembled by a Nd:YAG laser welding technique in conventional butterfly packages and their coupling efficiencies were 28%–72% without horizontal misalignment compensation.      

新型多芯光纤的模场特性分析

为了实现高功率、高亮度的光纤激光输出,研究了新型多芯光纤组束技术,基于大模场倏逝波,采用时域有限差分数值模拟方法,对多芯光纤(包含多根微纳纤芯或包含多根微纳芯和大芯径纤芯)的模场特性进行了数值仿真和理论分析。结果表明,以一定方式排列的微纳光纤束阵列中多根微纳纤芯可以很好耦合;当多根微纳芯和大芯径纤芯组束时,微纳纤芯能够有效地平坦模场。这一结果对于高功率光纤激光器和放大器的进一步发展很有帮助。     

High-Index-Layer Coating on a Lensed Fiber Endface for Enhanced Focusing Power

A new scheme for lensed fibers with a high focusing power is proposed. The new lensed fiber has a high-index layer coated (HILC) on a convex-shaped endface of a single-mode fiber (SMF). Numerical investigation shows that, by coating a 10-mum-thick film with refractive index of 3.7, the lensed fiber can contract the beam diameter of the propagating mode from 10.4 mum at the wavelength of 1.55 mum, to 1.2 mum. The enhanced focusing effect of the lensed fiber has been confirmed experimentally by coating an a-Si:H film on the lensed endface. The measured focused spot diameter was as small as 1.6 mum, much the same as the wavelength.     

Laser-to-fiber coupling scheme by utilizing a lensed fiberintegrated with a long-period fiber grating

An optical coupling scheme between a laser diode and a single-mode fiber utilizing a lensed fiber integrated with a long-period fiber grating is experimentally demonstrated and qualitatively analyzed. A long working distance of 110 μm and a coupling of 35% are obtained for a laser diode with an ellipticity of 2.5. The longitudinal and transverse tolerances at 1-dB excess loss are 26 and 2.5 μm, respectively