Efficient coupling of laser diodes to tapered monomode fibres with high-index end

The coupling efficiency between monomode fibres and laser diodes can be significantly increased by means of a high-index microlens which is attached on the cleaved end of a tapered monomode fibre. Coupling efficiencies of more than 50% can be attained.     

Distributed-index planar microlens array prepared from deep electromigration

Monolithic fabrication of a new distributed index planar microlens array by means of a deep electromigration technique in a glass substrate is reported. The array consists of distributed index lenses of 1.2 mm in diameter with 6.8 mm focal length. The focused spot is as small as 16 ?m for ?=0.63 ?m. The coupling efficiency of 60% to a multimode VAD fibre has been obtained.     

Microlens for efficient coupling between LED and optical fiber

A new fabrication method of a microlens is proposed that can be easily applied to optical devices and microlens systems. The proposed microlens is formed by self-surface tension and cohesion of UV curing material. Since the microlens is hardened by short time UV exposure, the fabrication process is very simple. Integration with surface emitting-light emitting diode (SE-LED) results in enhanced coupling to optical fiber with coupling efficiency larger than the conventional case by 1.5 times. We also made a hemispheric microlensed fiber using this method. Compared with a typical arc-lensed fiber and a flat-end fiber, the coupling efficiency is improved to 18% and 40%, respectively     

Design of the microlens arrays coupling with imaging fiber bundle

To ameliorate the disadvantages of imaging system coupled with imaging fiber bundle, a method by adding square aperture microlens arrays at both entrance and exit ends of the imaging fiber bundle is proposed to increase the system’s coupling efficiency. The expressions for solving the parameters of both ends’ microlens units are deducted particularly. The microlens arrays used for an infrared imaging fiber bundle with the single fiber diameter of 100 μm and core diameter of 70 μm are designed by this method. The simulation results show that compared with the system without microlens arrays, the fill factor of the imaging fiber bundle coupled microlens arrays system is increased from 44.4% to more than 90%, and the coupling efficiency is doubled too. So the design method is correct, and the introduction of microlens arrays into imaging fiber bundle coupled system is feasible and superior.     

基于微透镜阵外腔的光纤激光谱组束耦合效率分析

为了克服光纤激光外腔谱组束系统中增益带宽和透镜像差对组束阵元数量的限制,在系统中加入了微透镜阵。根据光束变换理论,建立了基于微透镜阵的光纤激光外腔谱组束系统的外腔耦合效率分析模型。通过数值模拟,对各种相关参数对耦合效率的影响进行了仿真分析。结果表明:微透镜阵的加入极大提高了阵元的耦合效率和系统的组束潜力;为了获得尽可能高的耦合效率,需要对离焦量进行合理配置并设计具有较长焦距的微透镜;横向对准误差是影响耦合效率的主要因素,对于宽度为10 mm的组束光纤阵列,为保证60%以上的耦合效率,在θy≤2 mrad的同时需将横向位置偏移量δy限制在10μm以内。     

Tunable fibre-extended-cavity laser

A tunable fibre-extended-cavity laser is demonstrated consisting of an InGaAsP superluminescent diode, a single-mode fibre with an integral microlens and a variable-period diffraction grating coupled to the fibre. A tuning range of 450 ? has been observed, limited by the gain spectrum of the gain medium.     

A 3-D planar microlens for an effective monolithic optical interconnection system

A three-dimensional (3-D) planar microlens with curved sidewalls was fabricated by using the recently developed 3-D diffuser lithography and the polydimethylsiloxane (PDMS) replication method. The sidewall of the fabricated 3-D planar microlens had a radius of curvature of 140 /spl mu/m, and a well-defined focal spot with a width of 1.5 /spl mu/m and a height of 3 /spl mu/m was observed. An excellent single-mode fiber-to-fiber coupling efficiency of 71% was demonstrated by applying the developed 3-D planar microlens, which displayed more than two times the coupling ability compared to that of a conventional two-dimensional planar microlens with straight sidewalls. Finally, it was verified that the coupling efficiency was little affected by variation in the process conditions used for the photoresist mold fabrication.     

红外双波叠层结构探测器微透镜阵列的设计

介绍了一种双波段红外探测器叠层结构微透镜阵列的设计,从实际光线角度进行建模,考虑微透镜加工线宽的要求,利用光学非成像理论的原理优化。并根据微透镜的衍射效率进行量化,分析了影响占空比因素的计算方法等,并对其进行了详细说明。该设计方法从实际入射光线建模,思路新颖,该方法经加工微透镜与探测器耦合后验证可行。给微透镜阵列的设计者一些启发,可用于其他多种叠层结构探测器的微透镜阵列设计。     

Small-junction-area GaInAs/InP pin photodiode with monolithicmicrolens

Reports on a back-illuminated GaInAs/InP pin photodiode with a monolithic microlens fabricated by the authors. The photodiode has both an ultrabroad bandwidth of 18 GHz and a high quantum efficiency of about 84%. It achieves this by using a small pin junction area while maintaining a large fibre alignment tolerance by incorporating an InP microlens. The photodiode capacitance was 20 fF for a junction diameter of approximately 15 μm     

Microlens formation on VAD single-mode fibre ends

The letter describes microlens formation process on VAD single-mode fibre ends by a chemical-etching/fire-polishing technique. No central dip in the VAD fibres leads to high-quality lens formation.     

Surface-mountable silicon microlens for low-cost laser modules

A surface-mountable silicon microlens that can be passively aligned in a silicon V-groove is proposed. The microlens has a diffractive optical element on the end facet of a semicylindrical structure whose diameter is identical to that of a single-mode fiber (SMF). The experimental result of coupling efficiency between a distributed feedback laser diode and SMF shows low loss (-3.0 dB) as determined using the microlens. Monte Carlo simulations indicate that the microlens is suitable for low-cost and high-performance optical modules for metro networks.     

32 channel WDM multiplexer with 1 nm channel spacing and 0.7 nm bandwidth

A high density WDM multiplexer capable of combining 32 channels spaced 1 nm apart onto a monomode fibre is reported. The multiplexer incorporates a microlens array to give a channel bandwidth of 0.7 nm. The wavelength range of operation is 1.5285 mu m to 1.5595 mu m, within the erbium fibre amplification range. The mean insertion loss over the 32 channels is 6.7 dB and the polarisation sensitivity is less than 0.7 dB.<>     

High-Power 1.06-$mu{hbox {m}}$ Near-Diffraction-Limited Planar Tapered Amplifier Injected With Seed Light Through a Fiber Biconical Microlens

We designed a 1.06-mum single-quantum-well (SQW) InGaAs/AlGaAs planar tapered amplifier that was injected with seed light of a fiber Bragg grating stabilized laser diode through a fiber biconical microlens. To increase the amplifier output, the microlens with approximately 3- and 11-mum radii on vertical and horizontal axes, respectively, provides high coupling efficiency between the laser diode and the amplifier. The microlens also controls propagation in the tapered gain area to suppress the filament formation. In addition, the small radii of the microlens reduce near-end reflection at the amplifier input to prevent parasitic laser oscillation of the amplifier. We demonstrated near-diffraction-limited output of 5.5 W with the beam quality factor M² of 1.5 by using a 3-mm-long amplifier having an optical confinement factor of 1.2%.     

硅基非球面柱面微透镜阵列制备方法

非球面柱面微透镜是一种重要的微光学元件,具有激光准直、聚焦、匀化等功能,在激光通信、光纤传感、激光雷达测距、激光泵浦等系统中具有广泛的应用。为了减小光电系统的体积、提升光纤性能,增大透镜数值孔径是一种常用的解决方案。提出采用折射率更大的硅作为低折射率石英基底的替代材料,使得微透镜在相同体积下数值孔径大幅提升,同时可以降低加工量从而提升制备效率。针对传统石英微透镜的制备方法不再适用硅基微透镜的问题,提出基于掩模移动曝光方法制备光刻胶非球面图案,使用多次涂胶和循环曝光方法,分别解决厚胶涂覆均匀性差及曝光掩模痕迹明显等问题,最终利用等离子体刻蚀技术进行图案转移传递,从而实现微透镜的制备。以数值孔径2.9的硅基非球面柱面透镜阵列为例开展实际制备工艺实验,所制备的微透镜列阵面型精度PV为0.766 μm,表面粗糙度Ra为3.4 nm,表面光洁与设计值符合较好,验证了制备方法的可行性。该方法有望促进非球面柱面微透镜列阵在紧凑化红外光电系统中的大规模应用。     

单模光纤与单模平面波导端面激励耦合的研究

本文研究了单模光纤与Ti内扩散LiNbO_3单模平面光波导的端面激励耦合问题。测量了它们的场强分布轮廓,给出了两者位置失配影响耦合效率的实验数据。在光纤输出端用光致抗触剂制作一个微透镜,缩小光纤输出的高斯光束束腰尺寸,耦合效率提高了1.47倍,与理论计算值相符。     

GaAs双异质结激光器和多模光学纤维的耦合

本文仅就GaAs双异质结激光器和多模光学纤维的耦合问题作一些讨论,以带有微透镜型的光学纤维为例,对耦合效率进行了计算.     

Characteristics of a hemispherical microlens for coupling between a semiconductor laser and single-mode fiber

A hemispherical microlens is fabricated on the end of a single-mode fiber by an electric arc discharge technique. It improves coupling efficiency between InGaAsP lasers with buried heterostructure geometry and single-mode fiber. The lowest coupling loss of 2.9 dB is achieved with the optimum lens radius of 8.5 μm. This loss is 4.4 dB lower than that with a butt joint. Experimental results of coupling efficiency and alignment tolerances in coupling with different lens radii in the range of3.5-17 mum are discussed in detail. The results are in good agreement with theoretical values derived by Gaussian beam and paraxial ray approximations.     

锥形光纤与楔形光纤的耦合

用实验方法测量了楔形光纤与锥形光纤的耦合效率,作出耦合效率随楔形光纤的半楔角及锥形光纤半圆锥角的变化曲线。从实验结果可以看出,楔形与锥形光纤的耦合效率随半楔角增加而增大。当半楔角由15.0°增大到30.3°,半楔角由44.9°增大到55.2°时,耦合效率曲线呈较快的上升趋势;当半楔角由30.3°增大到44.9°时,耦合效率曲线上升趋势变缓。当锥形光纤半圆锥角增加时,耦合效率也随着增大;并且随着楔形与锥形光纤的间距的减小而增大,在间距由0.10mm减小到0.03mm时,耦合效率曲线呈较快的上升趋势;在间距由0.03mm减小到0.01mm时,耦合效率曲线呈下降趋势。     

尖锥端光纤和半导体激光器的耦合

介绍了一种低反射高效率的尖锥端光纤和半导体激光器的耦合技术。应用模式耦合理论分析表明，这种尖锥端光纤的耦合效率可接近９０％，锥端反射损耗大于６０ｄＢ。因此，这种耦合技术既可以提高ＬＤ和光纤的耦合效率，又可以大大降低耦合反射对ＤＦＢ等激光器的影响。简单介绍了这种尖锥端光纤的制造技术，通过精密的磨抛加工，即可获得理想的尖锥端。用自行加工制备的尖锥端光纤与ＤＦＢ半导体激光器耦合，实际测量的耦合效率最大达７３．９％，反射损耗优于５０ｄＢ。     

光纤锥模场传输特性及光纤微透镜最佳位置研究

分析了两类光纤维（熔拉锥和腐蚀锥）的模场传输特性,引入了特征转换点,为降低模式耦合损失和增强聚焦效果,光纤锥微透镜制作的最佳位置,熔拉锥在靠近特征转换点处,腐蚀锥在锥端至特征转换点之间,并讨论光纤微透镜对高斯光束的聚焦。