High-power InAlGaAs-GaAs laser diode emitting near 731 nm

High-power, reliable operation of an InAlGaAs-based QW laser diode structure emitting near 731 nm and having a strained InAlGaAs active region is described. Threshold currents for coated 100 μm×1000 μm devices are 281 mA, and a peak power conversion efficiency of 41% is measured. Internal losses are measured to be 1.2 cm^-1. A system for fiber-coupling two-dimensional continuous-wave (CW) arrays of these devices is demonstrated     

InP-based optically pumped VECSEL operating CW at 1550 nm

We present a vertical external-cavity surface-emitting laser operating at 1550 nm. The laser comprises an InGaAsP-based gain element, with a resonant periodic gain structure on top of a distributed Bragg reflector, and a high reflectivity spherical mirror as the external reflector. Optical pumping is achieved using a 1250-nm fiber Raman laser. A maximum continuous output power of 70 mW was obtained under multitransverse mode operation at 233 K. Under single-mode operation, we obtained a maximum power of 60 mW with a beam quality factor M/sup 2/ less than 1.1.     

0.8 W optically pumped vertical external cavity surface emitting laser operating CW at 1550 nm

An InP based optically pumped vertical external cavity surface emitting laser has been designed and optimised for emission at 1550 nm. To overcome thermal limitations an intra-cavity synthetic diamond heatspreader is bonded to the gain structure. The laser produces 780 mW at -30/spl deg/C and 100 mW at 20/spl deg/C in a near Gaussian beam (M/sup 2/<1.2).     

High-power distributed Bragg reflector lasers operating at 1065nm

A report is presented on distributed Bragg reflector lasers emitting in excess of 700 mW in a single-spatial and single-spectral mode at 1065 nm. The threshold current of these devices is ~30 mA, there is an L-I slope of 0.74 W/A, and a sidemode suppression ratio greater than 30 dB. The current and thermal tuning are 0.016 A/mA and 0.7 A/degC, respectively.     

Tunable picosecond frequency-shifted feedback fiber laser at 1550 nm

A novel frequency-shifted feedback (FSF) fiber laser cavity is proposed and experimentally verified. The laser generates stable mode-locked pulses of <2 ps, mainly limited due to chirp induced by the frequency-shifting element (i.e., the acoustooptic modulator) on the pulses. Fourier transform-limited subpicosecond pulses were obtained by compensating this excess chirp using a piece of single-mode fiber SMF-28 outside the laser cavity. The unique cavity design also allow us to tune the pulse wavelength throughout the Er-gain band and the ability of the laser to self-start gives us the opportunity to characterize transient behavior of mode-locked pulses in an FSF fiber laser cavity.     

有线电视1550系统中掺铒光纤放大器的串联

有线电视系统通常采用1310nm或者1550nm的发射光波长.随着1550nm外调制光发射机成本的降低,1550nm光系统的优势越来越明显:传输距离长、衰减小、可以进行中继放大传输,减少机房内的设备数量从而降低用电量等.在1550nm光传输系统里,用来中继放大的光放大器得到了广泛的应用,然而随着串联级别逐渐增多,会导致信号质量的下降.本文根据一次实际故障,通过光放大器背靠背实验进行测试,分析光放大器的使用环境,对于光放大器放置位置的设计规划提供参考.     

有线电视光网络1550nm窗口三波混合试验

针对有线电视光网络传输系统应对三网融合业务发展的需要,对光网络1 550 nm窗口进行了三波混合试验,给出了低成本的三波混合试验方案,测试出不同输入状态下的传输指标,推荐出较为理想的三波混合方案和传输指标。     

High-power diode lasers with small vertical beam divergenceemitting at 808 nm

A new waveguiding scheme for high-power diode lasers based on high-index quarter-wave reflecting layers inserted into the cladding layers is presented. For 808 nm lasers, a small vertical far-field angle of 18°, a low threshold current density of 280 A/cm² and a high conversion efficiency of 50% are simultaneously obtained     

高功率半导体激光器光纤耦合模块

光纤耦合输出的高功率激光二极管模块具有体积小、光束质量好、亮度高等特点,在泵浦光纤激光器、材料处理、医疗仪器等领域都获得了广泛的应用.为了进一步提高光纤耦合激光二极管模块的输出功率,提出了基于多只激光二极管串联的光纤耦合方法.这种方法具有耦合效率高、光学元件加工简单等特点.利用两组反射镜,将多只高功率激光二极管输出光束经准直、复合、聚焦,耦合进光纤输出,根据激光二极管和光纤的相关参数设计了聚焦透镜.利用特殊加工的A1N材料作为过渡热沉解决了激光二极管的导热和相互之间的绝缘问题.采用这种方法将4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4.0 A时,光纤连续输出功率为11.6 W,耦合效率大于79%.     

1550nm有线电视传输系统在农村网络中的应用

详细阐述利用1550nm有线电视传输系统＂密集广播分配＂的特点,采用FTTLA组网技术建设农村有线电视网络的具体应用,尤其对二级光链路网络指标分配、设计要求做了具体说明,为农村有线电视网络＂村村通＂工程提出一个科学、安全、经济、可靠的设计方案。     

High-power, broad-band 1550 nm light source by tandem combinationof a superluminescent diode and an Er-doped fiber amplifier

A high-power (20-mW) broadband (21-nm-FWHM) 1.55-μm light source with small spectral modulation depth has been achieved by amplifying the output of a superluminescent diode (SLD) with an Er-doped fiber amplifier (EDFA). These characteristics are desirable for fiber gyroscope applications. The twin fluorescence peak problem is solved by operating the EDFA in the saturated region with an injected SLD signal     

High-power 783 nm distributed-feedback laser

A ridge-waveguide GaAsP/AlGaAs laser, emitting an optical power of up to 200 mW in a single lateral and longitudinal mode at a wavelength of 783 nm, is presented. The distributed feedback is provided by a second-order grating, formed into an InGaP/GaAsP/InGaP multilayer structure. The laser is well suited as a light source for Raman spectroscopy.     

High-power pulsed GaAs laser diodes operating at room temperature

The fabrication and characteristics of a high-power GaAs injection laser for room-temperature operation are described. A single laser emits 70 watts peak power from one facet at four times the threshold current. The diodes are fabricated from epitaxial wafers prepared by the solution-growth process. Scaling from work on low-power (7-watt) units to this high power has been accomplished by increasing the junction width, which requires general improvement in the crystalline quality and in the control of the doping. Data are given on the effect of doping density, crystal quality, and imperfections near the junction, as well as junction width. The reduced yield in high-power diodes, of which only one-third from a single batch give the desired output, is associated with filamentary lasing and with super-radiant walk-off modes, neither of which is under full control. Preliminary data on life tests show that long-lived units can be made, but that apparently identical units from the same batch show wide variations in the rate of degradation.     

Nonlinear distortions and compensations of DFB laser diode inAM-VSB lightwave CATV applications

The nonlinear distortions of a directly modulated laser diode applied to AM-VSB lightwave CATV systems are studied from the viewpoint of rate equations. A simple method for calculating composite second-order distortion (CSO) is proposed, which is called the quasidynamic approach. The contribution to nonlinearity from fiber dispersion and laser chirping is also discussed. The dependences on the variations of parameters of rate equations are investigated to determine the dominant factor for CSO degradation. This approach explains quite well the experimental results and suggests a method for constructing a predistortion circuit with at least 10 dB improvement     

Low-noise narrow-linewidth fiber laser at 1550 nm (June 2003)

We present a compact integrated fiber laser with more than 200 mW of output power. It combines polarized fiber output with very narrow linewidth of less than 2 kHz. The coherence length of the laser is measured to be longer than 5 km. The laser features high mode stability of less than /spl plusmn/10 MHz over hours. The relative intensity noise (RIN) spectrum is dominated by a peak at the relaxation oscillation frequency and is shot-noise limited otherwise. The RIN peak at 1 MHz is reduced to /spl sim/-130 dB/Hz by integrating a negative feedback circuit. In addition to thermal wavelength tuning, the laser frequency can be modulated at a bandwidth of up to 10 kHz via the piezoelectric effect.     

1550nm波段光纤CATV传输系统的噪声分析及组网

对1500nm波段光CATV噪声的产生的机制进行了讨论.重点分析了EDFA产生的噪声特性,对系统载噪比(CNR)与EDFA输入功率之间的关系和系统CNR与调制指数的关系进行了研究,得出了提高CNR的方案;对光CATV组网方案进行了讨论,给出了一个光CATV网络设计的实例.     

1550nm光纤CATV升级改造方案

随着湖北省有线电视网络SDH光纤主干线全省开通，为湖北地区信息基础设施建设提供了坚实的物质基础。为迎接对世纪信息化社会的到来，钟祥广电局预定对钟祥CATV按HFC750MHz升级改造。1环境与现状钟祥市地处江汉平原，区域面积4488（k叫’，24个乡镇场，506个自然村，约26...     

1550 nm全光纤单频脉冲光纤激光器

设计并实现了一种基于人眼安全波段的1550 nm全光纤化结构单频脉冲光纤激光器。激光器采用外腔稳频技术的单频半导体激光器作为种子源,其线宽1.8 kHz,功率20 mW。通过预放大器和声光调制器获得单频脉冲激光,并运用两级光纤放大器实现了线宽1.9 kHz、平均功率521 mW、脉冲宽度200 ns、重复频率10 kHz的单频脉冲光纤激光输出。输出脉冲峰值功率达260 W。输出端采用了双包层单模光纤,保证了输出激光的光束质量。整个激光器通过对种子光级联放大,结合放大器的增益控制,成功抑制了受激布里渊散射(Stimulated Brillouin Scattering,SBS)效应,消除了放大过程中噪声对线宽的影响,获得了线宽稳定的单频脉冲激光。     

Distributed feedback laser diode and module for CATV systems

Harmonic distortion of distributed feedback laser diodes (DFB-LDs) for analog transmission systems is investigated. It is shown that, under a modulation frequency of less than 1 GHz, the harmonic distortion depends on the nonlinearity of the light output power-current (P-I) curve under the continuous wave (CW) condition, which is determined by the coupling constant κ L, and that the distortion can be minimized at κ L~1. A 1.3 μm wavelength InGaAsP DFB-PPIBH (p-substrate partially inverted buried heterostructure) LD and its module, with low distortion by the control of a coupling constant, have been developed     

High-power single mode InGaAs/AlGaAs laser diodes at 910 nm

Single mode laser diodes have been fabricated from pseudomorphic InGaAs/AlGaAs quantum well epitaxial material operating up to 350 mW CW. The laser output is a single transverse and longitudinal mode to 180 mW, while the spectral output is centred near 910 nm.<>