LD激光与单模光纤耦合时的失准容忍度分析

本文导出了ＬＤ激光与带端面微透镜的单模光纤直接（ＳＭＦ）耦合时的失准容忍不变量－失准容忍面积。并指出横向与角向的中心失准容忍度分别与ＬＤ的模斑尺寸、ＳＭＦ模斑对应的远场发散角成正比；而横向和角向的最大失准容忍量却分别与ＳＭＦ的模斑尺寸、ＬＤ的远场发散角成正比。最大失准容忍量是中心失准容忍量的Ｋ倍。     

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.     

Optical coupling characteristics of laser diodes to thermally diffused expanded core fiber coupling using an aspheric lens

A discussion is presented of the optical coupling characteristics of a 1.3 mu m laser diode to a thermally diffused expanded core (TEC) single-mode fiber coupling using an aspheric lens. The misalignment tolerance width for a 0.5 dB loss increment of the expanded core fiber was enlarged to 8.4 mu m from 1.9 mu m of a nonexpanded core fiber without a remarkable coupling-loss increase. The TEC fibers will make the LD module assembly easier, and reduce the assembly cost.<>     

基于偏振复用技术的激光二极管光纤耦合方法

光纤耦合输出的高功率激光二极管(LD)模块作为光纤激光器的抽运源已经得到了广泛应用。为了进一步提高光纤耦合激光二极管输出功率,提出了利用激光二极管输出光束的线偏振特性,采用偏振复用技术,将两只高功率激光二极管输出光束经准直、复合、聚焦的光纤耦合方法。利用光线追迹法,分析了圆柱透镜对激光二极管发散光束的准直特性,并讨论了柱透镜的安装距离对准直性能的影响。根据激光二极管和光纤的相关参数设计了聚焦透镜组。采用这种方法将两只输出波长为980 nm的高功率激光二极管输出光束耦合进数值孔径0.22,芯径100μm的多模光纤中,当工作电流为4.5 A时,光纤激光连续输出功率为6.36 W,耦合效率大于78%。     

LD Redundancy System Using Polarization Components for a Submarine Optical Transmission System

An LD redundancy system having one cold standby laser diode is proposed to improve reliability in submarine optical transmission systems. This system makes use of the intrinsic laser polarization and consists of two LD modules and a polarization coupler connected by polarization maintaining (PANDA) fibers. The optical power insertion loss of this LD redundant system is 5.5 dB, including coupling loss between the laser diode and PANDA fiber. This LD redundant system will be applied in submarine optical repeaters.     

LD redundancy system using polarization components for a submarine optical transmission system

An LD redundancy system having one cold standby laser diode is proposed to improve reliability in submarine optical transmission systems. This system makes use of the intrinsic laser polarization and consists of two LD modules and a polarization coupler connected by polarization maintaining (PANDA) fibers. The optical power insertion loss of this LD redundant system is 5.5 dB, including coupling loss between the laser diode and PANDA fiber. This LD redundant system will be applied in submarine optical repeaters.     

空心透镜导管的模拟与设计

采用大口径、高功率激光二极管(LD)阵列的大型全固化二极管抽运激光系统(DPSSLs)能够产生高功率、大能量、高重复频率的优良激光。为了实现对介质的高效抽运，将空心透镜导管应用于大口径高功率激光二极管阵列耦合系统。基于三维光线追迹的数值计算方法，编制了LD纵向抽运耦合系统模拟软件，对空心透镜导管进行模拟与设计，使系统耦合效率超过90％的同时，增益介质表面抽运场具有良好的均匀性，实现了对介质的高效均匀抽运；同时通过改变空心透镜导管的参数进行模拟比较，得出了空心透镜导管设计的经验公式，为大型DPSSLs耦合系统的设计提供了有益的参考。     

LD抽运腔内倍频456nm激光阈值理论分析与实验研究

从准三能级激光系统阈值理论出发,分析了影响激光阈值的几个因素。实验中采用标称输出功率为3W的LD,端面抽运掺杂浓度为0．15atm．％Nd：GdVO4晶体,利用曲率半径为30mm的输出镜,使用LBO晶体Ⅰ类相位匹配倍频获得了阈值大约为0．42mW的456nm蓝色激光输出。在抽运功率为1．9W时,最高功率达82mW,光-光转换效率为4．32％。为具体比较晶体掺杂浓度、输出镜曲率半径对激光阈值产生的影响,又采用尺寸相同,掺杂浓度为0．25atm．％的晶体以及曲率半径为50ram的输出镜进行了对比实验分析。结果表明,较低掺杂浓度晶体和较小曲率半径输出镜的激光阈值较低.     

A 1.3-/spl mu/m wavelength laser with an integrated output power monitor using a directional coupler optical power tap

A 1.3-/spl mu/m Fabry-Perot laser with a directional coupler power tap inside the laser cavity, used for diverting optical power to an integrated waveguide monitoring photodetector is demonstrated. The monitoring detector provides photocurrent which is linear with the front facet output power, with responsivity as high as 0.37 mA/mW, depending on the length of the directional coupler coupling region.     

Single-mode fiber WDM unit for duplex subscriber link using asubstrate with embossed alignment grooves

A wavelength division multiplexing (WDM) unit for single-mode fiber (SMF) duplex transmission, with light source, photodiode (PD), and WDM coupler arranged on a common substrate, is described. Using a tolerant optical design, the optical elements, e.g. lenses and fibers, are positioned in embossed high-precision V grooves without active adjustments. Only the light source, a laser diode (LD) or an edge-emitting LED (ELED), must be aligned for optimum coupling and fixed by laser welding. Typical values of LD-to-fiber and fiber-to-PD coupling loss and crosstalk are 5 dB, 1.2 dB, and -44 dB, respectively. Hence, in spite of the potentially low-cost design, the optical performance of the device is virtually competitive with separated transmitter and receiver units     

Low-loss laser diode module using a molded aspheric glass lens

The fabrication and characteristics of a 1.3-μm laser diode (LD) module for single-mode fiber using a molded aspheric glass lens is discussed. An average coupling loss of 2.2 dB with a standard deviation of less than 0.5 dB after thermal heat cycling tests was achieved. The average assembly loss was 0.24 dB. The LD module demonstrated stability during thermal and heat cycling tests from -10 to 60°C     

An effective nonreciprocal circuit for semiconductor laser-to-optical-fiber coupling using a YIG sphere

A practical nonreciprocal optical circuit for laser-diode (LD)-to-optical-fiber coupling in the 1.3-μm wavelength region is described. It consists of a yttrium iron garnet- (YIG) sphere graded-index (GRIN) rod lens and a polarizer. The YIG sphere can function not only as a Faraday rotator but also as an effective coupling lens. High coupling efficiency of more than -5 dB for a single-mode fiber, and more than -2 dB for a multimode fiber, is easily achievable. Alignment sensitivities and coupling characteristics of the proposed circuit are also discussed theoretically and experimentally. The increase in LD relative intensity noise (RIN), caused by light injected into the LD, is estimated using the reciprocal characteristics of LD-to-single-mode-fiber coupling. By comparing the LD-RIN increase in the proposed non-reciprocal circuit with that of the reciprocal, high isolation of about 32 dB is confirmed. The fact that reflected light from the proposed circuit has little influence on LD characteristics is also clarified.     

Improved coupling efficiency of a strained InGaAs-AlGaAs quantum-well laser into a fiber Bragg grating

We describe a highly efficient coupling of up to 78% into a single mode fiber (SMF) by utilizing a low-divergence-angle InGaAs-AlGaAs laser and a new high-NA aspheric lens, resulting in the coupled optical output of over 300 mW with a kink-free performance. The kink-free 300 mW of fiber-coupled power is the largest power reported from a diode laser wavelength stabilized using a fiber Bragg grating. A 3% fiber Bragg grating makes the optical output stabilize at a wavelength of 1.016 /spl mu/m for an optical output power up to 310 mW and without any distinct decrease of the optical output. The coupling tolerance for lateral offsets is improved by utilizing a thermal-diffused expanded-core technique even in the case of using a high-NA coupling aspheric lens. We have also achieved a 300-mW fiber-coupled wavelength-stabilized InGaAs-AlGaAs semiconductor laser butterfly module using a fiber Bragg grating.     

激光成像系统中高耦合效率单模光纤耦合器设计

在三维激光成像系统中,其性能表现绝大部分决定于器件接收背反射光能幅度的大小,以及耦合器中空间光到光纤纤芯的光耦合效率的高低.为了增加耦合器中激光能量到纤芯内的耦合效率,提出了一种新型非球面透镜到锥形光纤头的耦合器的设计,得到了该耦合器中耦合效率的解析表达式.通过优化耦合透镜的倒相对孔径,对应波长为1 310 nm和1 ...     

A novel one step integration of edge-emitting laser diode withmicro-elliptical lens using focused ion beam direct deposition

An edge-emitting laser diode (LD) integrated with a microlens on its emitting surface for the purpose of collimating and fiber coupling is introduced in detail in this paper. A micro-elliptical lens is adopted for the integration in terms of divergence angle in both parallel and transverse directions. The lens with dimensions of 50 μm×30 μm×4 μm is microfabricated on the emitting surface of the laser diode with operating wavelength of 635 nm directly by focused ion beam (FIB) deposition function. The SiO₂ deposition is realized by programming of the FIB machine. It is shown by test results that the focused spot size in the parallel and transverse propagation directions are 7.9 and 9.1 μm (at site of 1/e²), respectively, and the coupling efficiency of the compact and miniaturized system can reach as high as 71%. Measured far-field angles (full angle) with the microlens in both parallel and transverse directions are 2.2° and 1.2°, respectively. Compared with the original divergence angles of 31° and 14° without the micro-elliptical lens, they were greatly reduced by this method     

Characteristics of High-power GaAs Laser Beams and Their Coupling with Fibers

The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.     

115-W Tm:YAG diode-pumped solid-state laser

A compact diode-pumped Tm:YAG laser capable of generating greater than 100 W of CW power at 2 μm has been demonstrated. A scalable diode end-pumping architecture is used in which 805-nm radiation, coupled to the wing of the Tm³⁺³H₆-³H ₄ absorption feature, is delivered to the end of the laser rod via a lens duct. To facilitate thermal management, undoped YAG end caps are diffusion bonded to the central doped portion of the laser rod. For 2% and 4% Tm-doped rods of the same length, the lower doping level results in higher power, indicating that cross relaxation is still efficient while offering lower thermal stress and reduced absorption at the laser wavelength. Output powers for various output coupler reflectivities are compared to the predictions of a quasi-three-level model. Thermal lensing, cavity stability, and stress-induced birefringence measurements are described. The beam quality was analyzed with the 2% Tm-doped rod and a flat output coupler, yielding M² values of 14-23     

波前分割DOE阵列半导体激光器光束的品字形整形

半导体激光器（LD）输出光束受工作电流、个体差异的影响,发散角、输出光强出现波动。常规衍射光学元件（DOE）的激光光束整形设计只针对特定的输入输出光场,使用宽容度比较小。文中在LD 的整形中利用DOE 阵列化的处理,输入光场被分割成许多小单元,不同强度的光重新在成像平面内预定的区域内叠加,实现对光束的整形。用均匀平面波设计阵列DOE 每个单元,把高斯分布的球面波整形成品字形光强分布,衍射效率为90.53%,均匀性大约为96%;发散角在快、慢轴方向上2~16的范围内变化,均匀性为95.8%以上、衍射效率为90%以上;在离焦量16 m 内,光束质量变化不大。阵列DOE 提高了LD 光束整形系统的稳定性。     

WDM experiment using 1300/1500 nm dual-wavelength LED for single-mode fibre transmission systems

A wavelength-division-multiplexing transmission experiment using a 1300/1500 nm dual-wavelength LED modulated at 140/560 Mbit/s over 10 km of single-mode fibre has been demonstrated. This dual-LED device has a 9 ?m emitter spacing between the active facets with a coupling loss of 2.3 dB through a lens/fibre coupler. The chromatic dispersion penalty for the 1500 nm channel at 560 Mbit/s was about 6-5 dB and the electrical crosstalk penalty was 2.5 dB.     

Efficiency of quasi-optical couplers

Millimeter-wave devices are often coupled to radiation by means of a feed antenna placed at the focus of a primary lens or mirror, a technique known as “quasioptical coupling”. A general expression for the efficiency of such a coupler is derived. The efficiency of such a coupler depends on the relationship of the feed antenna pattern to the numerical aperture of the primary lens. An approximate general rule for coupler design is obtained. This rule is as follows. Let θ_o be the angle between the direction in which the feed pattern is maximum and the direction in which the pattern intensity has one-half its maximum value. Then the optimum numerical aperture of the primary lens is approximately sin (1.67 θ_o). The effects of focussing errors and lens aberrations can also be calculated by this technique.