激光二极管线列阵与多模光纤列阵的光纤耦合

利用一段数值孔径(NA)较小的多模光纤作为一个低成本的微透镜,对激光二极管线列阵的大数值孔径方向准直,将激光二极管线列阵的输出光束耦合到多模光纤列阵中.激光二极管线列阵每个发光单元的光分别耦合到光纤列阵的单根光纤中.总的耦合效率和输出光功率分别为75%和15W.     

激光二极管线列阵与多模光纤列阵的光纤耦合

利用一段数值孔径(NA)较小的多模光纤作为一个低成本的微透镜,对激光二极管线列阵的大数值孔径方向准直,将激光二极管线列阵的输出光束耦合到多模光纤列阵中.激光二极管线列阵每个发光单元的光分别耦合到光纤列阵的单根光纤中.总的耦合效率和输出光功率分别为75%和15W.     

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.     

掺镱多模双包层光纤激光器弯曲选模研究

为了使大芯径多模双包层光纤激光器实现基模输出以抑制高功率双层光纤激光器中的非线性效应,采用将大芯径的多模双包层光纤适当弯曲进行选模使双包层光纤激光器获得单模激光输出的方法,进行了理论分析和实验验证,取得了大芯径多模双包层光纤内包层折射率、纤芯半径、光纤内传输信号光波长、光纤弯曲半径等因素对弯曲损耗及激光器输出光场模式影响的数据,并采用国产掺镱多模双包层光纤进行了弯曲选模实验,实现了多模光纤激光器的单模输出.结果表明,激光器最大输出功率达9W,斜率效率达17.3%,输出为基模.这一结果对大芯径多模双包层光纤激光器的选模是有帮助的.     

Efficient laser diode side pumped neodymium glass slab laser

The authors report efficient pulse operation of an Nd:glass slab laser-side-pumped by laser diode arrays. 7.5 mJ output and a slope efficiency of 29% were obtained with 35 nJ pump energy at 0.8 μm in 200 μs pulses. The wide absorption band at 0.8 and low laser loss in this phosphate glass allow for efficient pump light absorption and straightforward scalability to high power. The authors demonstrate 22% optical efficiency in a long pulse, multimode diode pumped laser oscillator based on a phosphate laser glass, LHG-8, highly doped with Nd ₂O₃. The strong and wide absorption bands in such phosphate glasses allow efficient pumping while somewhat relaxing the expensive wavelength selection requirements for laser arrays compared with crystal line host materials. With such materials, smaller slab thickness or rod diameters that are feasible with Nd:YAG can be used in the side-pumping geometry     

Arrayed Multimode Fiber to VCSEL Coupling for Short Reach Communications Using Hybrid Polymer-Fiber Lens

We report the novel method that can give high coupling efficiency between a vertical-cavity surface-emitting laser (VCSEL) array and a multimode optical fiber ribbon by using a hybrid-polymer-fiber lens technique. The coupling efficiency as high as 91% was achieved by optimizing the polymer lens curvature for the single source to the single fiber case. The longitudinal and the transverse coupling tolerances were enhanced with the introduction of a coreless silica fiber (CSF) segment between the fiber and the lens tip. The tradeoff between the high coupling efficiency and the large tolerance was experimentally observed. The technique was further applied to the coupling between a four-channel VCSEL array and a four-core fiber ribbon for short reach applications. The procedure of fabrication and the analysis of their optical characteristics are reported.     

A high-efficiency 50 GHz InGaAs multimode waveguide photodetector

A side-illuminated p-i-n photodetector with a multimode waveguide structure is proposed. Numerical and experimental results show that higher-order mode lights greatly enhance the coupling efficiency between the waveguide photodetector (WGPD) and a fiber, which leads to a high external quantum efficiency. The multimode WGPD has the major advantage that the external quantum efficiency and bandwidth can be derived independently of each other because the multimode waveguide structure can be designed without deteriorating electrical properties. The fabricated WGPD has an external quantum efficiency of 56% without AR coating and 68% with AR coating, and an electrical frequency 3 dB greater than 50 GHz at a 1.55-μm wavelength     

Influence of bending diameter on output capability of multimode fiber laser

The output capability of large mode area (LMA) multimode fiber laser depends on the fiber bending. To study the relationship, the output capability of multimode fiber laser was measured under various bending diameters, and it was also theoretically calculated. Measured respectively were the beam quality factor M2, by means of knife edge for the different bending diameters of LMA fiber, and the slope efficiency. When the bending diameters 285, 195 and 130 mm were used, zthe corresponding beam quality factors were 2.88, 1.82and 1.67 with the slope efficiency at 39%, 35% and 34%,respectively. In addition, for the LMA multimode fiber used in the experiment, losses of different modes were calculated theoretically under various bending diameters.The experimental results correspond to the calculated results.     

Optical sensor for temperature measurement using bimetallic concept

In this paper, we report an optical fiber sensor for measuring temperature based on bimetallic concept. The sensor is designed by following the basic principle of Fabry–Perot interferometer and theoretical detail of the sensor has been outlined here with a numerical study. An important feature of the proposed sensor is that the fabrication will be done on a commercial multimode optical fiber. The Micro-Electro-Mechanical Systems (MEMS) based fabrication process could be performed directly on a multimode optical fiber end face which will eliminate the need for adhesive in packaging. The sensor could be fabricated as sensor arrays for micro level applications. The potential application of the proposed optical sensor includes biomedical applications, nano research, microfluidics, and other MEMS devices.     

弯曲直径对多模光纤激光器输出性能的影响

大模场面积(LMA)多模光纤激光器的输出性能与光纤的弯曲程度有关。为研究两者之间的关系,在光纤不同弯曲直径下,对多模光纤激光器的输出性能进行了实验测量和理论计算。采用刀口法测量了不同弯曲直径下的激光光束质量因子M~2,并对每种情况下光纤激光器的斜率效率进行了测量。光纤弯曲直径分别为285 mm, 195 mm和130 mm时,多模光纤激光器光束质量因子M~2为2．88,1．82和1．67,斜率效率为39％,35％和34％。另外,对于实验所采用的大模场面积多模光纤,理论计算了各模式损耗与光纤弯曲直径的关系。     

Long-wavelength monolithic VCSEL arrays with high optical output power

Two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays at 1.55 /spl mu/m wavelength with parallel operation of single- or multimode devices are presented. 3/spl times/3 VCSEL arrays show maximum output powers beyond 30 mW and conversion efficiencies as high as 22%.     

激光在锥形多模光纤中的耦合效率与传输模式

基于光线追迹的方法建立了典型锥形多模光纤的传输模型,结合激光干扰设备激光的特点,模拟计算了激光在锥形多模光纤中的耦合效率和传输模式,并设计进行了光学实验。仿真和实验结果表明:高斯激光光斑经锥形多模光纤传输后为圆环形光斑;耦合效率随激光入射角的增大而减小,减小的速率随入射角的增大而减小。为解决圆环形光斑分布,提出了将输出端连接的圆柱形光纤弯曲一定角度的方法,该方法可以将光斑改善为二维正态分布的光斑,理论耦合效率近80%。该研究为激光干扰设备的干扰激光直接介入激光制导武器对抗半实物仿真系统提供了理论和实验支持。     

Multimode oscillation Q-switched erbium-doped fiber laser with a few-mode fiber cavity

We propose and demonstrate experimentally a multimode oscillation Q-switched erbium-doped fiber laser with a few-mode fiber cavity. The different coupling processes of reflection peaks of fiber Bragg gratings (FBGs) which act as cavity mirrors allow the different oscillating states. We obtain microsecond light pulse output states whose oscillation and output beams have different mode compositions, including high order mode. Such a structure enables the high order mode oscillation in the whole cavity with an all-fiber structure, which has potential applications in mode-division multiplexed systems and research of multimode nonlinear effect.     

Passive alignment optical subassemblies for military/aerospacefiber-optic transmitter/receiver modules

Under the DARPA sponsored Avionics Optoelectronic Module Technology program, new passive alignment carrier (PAC) optical subassemblies (LED-PAC and PIN-PAC) ruggedized for military/aerospace avionics fiber-optic transmitter and receiver applications have been developed, LED-PAC and PIN-PAC silicon micro-optical bench substrates were fabricated together on a 5 in diameter silicon wafer via multistage photolithography, thin-film, and substrate processing. Alignment v-grooves designed for passive optical alignment of 100/140 μm multimode optical fiber to the optoelectronic devices were terminated by solder locking the fiber to the silicon PAC substrates. The LED-PAC comprising a surface emitting LED die-bonded onto a novel precision molded AM submount passively mounted onto the silicon microbench achieves the required high coupling efficiency to 100/140 μm multimode optical fiber to meet stringent avionics transmitter output power requirements. The 100/130 μm multimode optical fiber-pigtailed PIN-PAC with a refractive lens etched into the p-i-n photodiode backside surface exhibited responsivities greater than 0.8 A/W at 1.3 μm wavelength. The LED-PAC and PIN-PAC optical subassemblies integrated with Boeing ARINC 636 (FDDI) transmitter and receiver thick film multichip (MCM-C) circuitry are capable of meeting both ARINC 636 and FDDI physical layer requirements     

大功率固体激光器高效率光纤耦合

光束质量参数对大功率固体激光器光纤耦合系统的设计起着关键作用。大功率固体激光器输出的为多模激光束,引入等效基模光束来计算多模激光束的光束质量是一种有效的方法,并定义包含光斑能量98%的光斑半径为束宽,以此计算多模激光束的光束质量,是准确有效的。结合大功率固体激光器的光纤耦合原理和光束变换理论设计了高效耦合系统,并对系统内透镜的通光孔径及焦距等参量做了数值优化。实验证明,此光纤耦合系统能够进行大功率固体激光高效率耦合,成功地实现了输入功率为2000W时,耦合效率大于94%的激光输出,并给出了光纤耦合的效率曲线及分析。     

Microlenses self-aligned to optical fibers fabricated using thehydrophobic effect

We report a means of fabricating microlenses on transparent spacers that are self-aligned to optical fibers. The lenses so formed have f-numbers (f s) as low as f/1.55 and can be fabricated with minimal processing steps. Lenses can be fabricated desirably “over-sized,” with input apertures larger than operational beam diameters, The lenses deviate from spherical by as little as ±80 nm over the middle 90% of their surfaces, and are diffraction limited when used in their paraxial regions. Previous work suggests that arrays of such lenses can be fabricated in parallel with good uniformity (Δf/f~±5.9% for a 15×15 array of 500 μm f/1.4 lenses), stability, and reproducibility (average f s are reproducible to within 3.5%). Although coupling efficiencies have not been measured, these values suggest that the lenses are of sufficient quality for a variety of multimode fiber applications     

大功率激光二极管高亮度、高功率密度光纤耦合

将条宽为100μm,有源区厚度为1μm的大功率激光二极管(LD)的输出光束高效地耦合到芯径是50μm的多模光纤中,得到了高亮度、高功率密度的光纤输出.功率密度高达3.6×104W/cm2,耦合效率为70%.LD输出光束的发散角较大并且存在较大的像散,因此耦合系统中需要结构复杂、性能可靠的微透镜.采用在一个玻璃衬底上,具有两个不同曲率半径的双曲面透镜实现LD与多模光纤的耦合.     

Highly efficient 40 GHz waveguide InGaAs p-i-n photodiode employing multimode waveguide structure

The authors describe the design procedure of a highly efficient waveguide p-i-n photodiode. The efficiency of the waveguide InP/InGaAsP ( lambda /sub g/=1.3 mu m)/InGaAs/InGaAsP ( lambda /sub g/=1.3 mu m)/InP p-i-n photodiode is calculated using the step-segment method and overlap-integral between the optical field of a fiber and that of the photodiode. A remarkably high coupling efficiency to a fiber can be obtained by using a multimode waveguide structure. The fabricated device has an external quantum efficiency of 68% as well as 3 dB bandwidth of higher than 40 GHz at a 1.55 mu m wavelength.<>     

Generation of 9.3-W multimode and 4-W single-mode output from 7-cm short fiber lasers

We generate 9.3-W continuous-wave 1535-nm multimode output from a 7.0-cm short-length Er-Yb codoped phosphate fiber laser. A slope efficiency of 29% is obtained at pump powers below 27 W. Very high output power per unit fiber length of 1.33 W/cm is achieved. From another 7.1-cm Er-Yb codoped fiber laser, 4.0-W single-transverse-mode output with M/sup 2//spl ap/1.1 is generated.     

Design of wavelength-switching erbium-doped fiber lasers with a multimode fiber Bragg grating using spatial-mode excitation and selection techniques

A multimode fiber Bragg grating (MMFBG)-based wavelength-switching erbium-doped fiber laser and its application in displacement sensing is proposed and demonstrated. According to the spatial-mode distribution in the multimode fiber (MMF), the modes reflected by the MMFBG at different wavelengths build a wavelength-dependent mode field on the transverse plane of the MMF. By varying spatial-launching position of the single-mode fiber against the MMFBG to achieve different mode group excitation and selection, single-wavelength lasing at 31 discrete wavelengths has been realized over a wide wavelength range.