10GHz低抖动增益开关DFB激光器

采用国产管芯,利用增益开关效应获得了10GHz超短光脉冲.利用自注入的方法,采用最简单的结构,减小了增益开关DFB激光器光脉冲的时间抖动,使10GHz光脉冲的时间抖动小于840fs.研究了光脉冲抖动量对温度变化及微波驱动频率的敏感性.利用线性压缩和梳状色散渐减光纤链获得10GHz、5ps无基座光脉冲.     

10GHz低抖动增益开关DFB激光器

采用国产管芯,利用增益开关效应获得了10GHz超短光脉冲.利用自注入的方法,采用最简单的结构,减小了增益开关DFB激光器光脉冲的时间抖动,使10GHz光脉冲的时间抖动小于840fs.研究了光脉冲抖动量对温度变化及微波驱动频率的敏感性.利用线性压缩和梳状色散渐减光纤链获得10GHz、5ps无基座光脉冲.     

GS-DFB半导体激光器的光自注入技术

报道了一种光脉冲自注入的新方法 ,它能使增益开关 DFB激光器输出光脉冲的时间抖动从 5.7ps减小到 1.2 ps,分析了注入光延迟时间及功率对时间抖动的影响 ,指出为取得抑制时间抖动的最佳效果 ,必须选择合适的反馈光脉冲延迟时间和适当的反馈光功率。实验中观察到在增益开关 DFB激光器光脉冲建立期间注入反馈光时 ,输出光脉冲会发生严重畸变。     

可调谐双波长低抖动增益开关光脉冲的产生

提出了一种产生可调谐双波长低抖动超短光脉冲的新方法。采用外光注入法来降低增益开关F-P激光脉冲的时间抖动,实现了脉冲光谱的双波长可调谐输出。实验中利用两个多量子阱DFB激光器作为外部种子光源,通过温度控制和偏振态调节使外部种子光有效地耦合到增益开关F-P激光器中,输出的光脉冲时间抖动(均方根)从2.57ps降低至1.06ps,双波长的边模抑制比可达25dB。通过改变DFB激光器和F-P激光器的工作温度,可实现波长从1540nm到1560nm的可调谐输出。     

高消光比超短脉冲产生的实验研究

实验研究了一种高消光比短脉冲的产生技术。利用色散补偿光纤线性压缩由增益开关分布反馈激光器出射的光脉冲。而后利用电吸收调制器的非线性吸收特性同步调制光脉冲。利用这种方法在实验上产生了重复频率为10GHz，脉宽为10．4ps，抖动小，高消光比，无基座的短脉冲。此种技术可以应用于40Gbit／s的光时分复用系统中，同时也说明电吸收调制器具有同号脉冲整形功能。     

低时间抖动的增益开关型被动调Q激光器

被动调Q激光器的输出抖动一般较大,为了降低这一输出时间抖动,同时实现激光器的小型化,可以根据增益开关工作原理,利用电源控制抽运功率密度变化,实现被动调Q情况下的增益开关.根据这一原理研制了环形激光二极管(LD)抽运增益开关调Q激光器.这种新型被动调Q激光器的输出能量为30 mJ,输出脉冲宽度约16 ns.实验中将传统的两套抽运源减少为一套,通过控制电源波形直接形成抽运功率的增益台阶脉冲,减少了影响时间跳动的因素.多发次统计测量结果表明,激光脉冲与电源输出外触发信号的时间抖动小于1 μs.根据测量的抽运预脉冲功率稳定性和阶跃脉冲的瞬时抽运功率计算的输出抖动与实验结果基本相符.     

1.5μm高重复率超短光脉冲的产生

利用增益开关技术产生了1.5μm波长的高重复率超短光脉冲,其重复率从2.2GHz到3.5GHz,脉宽小于50ps。     

10 GHz超低抖动光短脉冲源

报道了一种新型的重复频率为10 GHz,脉宽为5.3 ps,抖动为184 fs的高稳定光短脉冲源.将大信号调制半导体激光器产生的10 GHz光脉冲,先送入LiNbO3电光相位调制器增强负啁啾,并使光谱进一步展宽,再通过色散补偿光纤(DCF)压缩脉冲啁啾,可得到光短脉冲.由于大信号调制激光器输出的光脉冲本身具有负啁啾,而通过相位调制器的光脉冲在不同的时间间隔内既有正啁啾也有负啁啾,通过适当调整进入相位调制器的光脉冲时延,使其通过相位调制器后累加产生更大的负啁啾,再利用正色散光纤压缩啁啾,从而得到低抖动且无基座的光短脉冲.     

增益开关F-P激光器抖动的计算和测量

为了能够精确测量增益开关激光脉冲的抖动,应用傅里叶变换和自相关函数．理论分析了谐波频谱分析法测量激光脉冲抖动的数学模型、测量原理。修正了David A．Leep等人建立的基于功率谱测量脉冲抖动的误差,推导出了普适的测量激光脉冲抖动的数学表达式,并数值模拟了不同情况下激光脉冲功率谱的表现形式;利用谐波频谱分析法测量了外连续光注入下增益开关F-P激光脉冲的抖动,时基抖动为0．905ps、振幅噪声为2．83％,并与取样示波器的测量结果进行比较。结果表明在脉冲抖动较小、且重复频率较低的情况下,利用谐波频谱分析法测量脉冲抖动具有更高的精确度。其精确度可以达到飞秒量级。     

雪崩模式下的体结构GaAs光导开关

利用能量较低的脉冲激光二极管,在较高场强下触发GaAs光导开关,使其工作于雪崩模式,从而产生纳秒上升前沿的快脉冲电压。GaAs光导开关采用垂直体结构设计,芯片厚度为2 mm,电极形状分别为圆环和圆面,触发光脉冲从圆环穿过。快脉冲产生由同轴Blumlein脉冲形成线完成。对基于GaAs光导开关的同轴Blumlein脉冲线进行了模拟仿真和实验,当充电电压超过8 kV(40 kV/cm)后,开关开始了雪崩工作模式。当充电电压约为15 kV(75 kV/cm)时,在50 Ω负载上获得了约11 kV的脉冲电压,实验波形与仿真波形一致。对开关抖动进行了测试,其测试结果显示开关充电电压对抖动影响很大,随着开关偏压增加,开关抖动减小,开关获得了最小抖动约700 ps。     

DFB激光器调制特性ANN建模与设计

通过研究分布反馈式(DFB)激光器调制特性的速率方程，推导了调制特性的解析表达式，建立了调制特性神经网络(ANN)模型，计算机仿真与理论分析的结果相吻合。用此模型对激光器结构进行了仿真设计，得到的结果对激光器的生产设计具有重要的指导意义。     

AlGaAs/GaAs visible distributed feedback laser operating at 770 nm

A visible-light AlGaAs/GaAs DFB laser with practical characteristics oscillating at 770 nm has been fabricated by using two-step liquid phase epitaxy for the first time. Threshold current of 90 mA measured at room temperature is satisfactorily low for its simple oxide stripe structure. The same DFB mode oscillation without mode hopping has been maintained in a considerably wide range of temperature. The results show a possibility of realising a high-performance DFB laser in the visible-wavaelength region.     

1.3-μm GaInNAs-AlGaAs distributed feedback lasers

Room temperature continuous-wave operation of 1.3-μm single-mode GaInNAs-AlGaAs distributed feedback (DFB)-lasers has been realized. The laser structure has been grown by solid source molecular beam epitaxy (MBE) using an electron cyclotron resonance plasma source for nitrogen activation (ECR-MBE). Laterally to the laser ridge a metal grating is patterned in order to obtain DFB. The evanescent field of the laser mode couples to the grating resulting in single-mode DFB emission. The continuous wave threshold currents are around 120 mA for a cavity with 800-μm length and 2 μm width. Monomode emission with side-mode suppression ratios of nearly 40 dB have been obtained     

A method to determine the above-threshold stability of distributedfeedback semiconductor laser diodes

An analysis of the above-threshold stability of distributed feedback (DFB) semiconductor laser diodes (LD's) is presented. It is based on a numerical model which takes into account effects of spatial hole burning (SHB) and the nonlinear gain coefficient. In the analysis, the Newton-Raphson (NR) technique has not been used, and no functional derivative is required. Taking into account the presence of another nonlasing mode, the single-mode stability of the DFB laser diodes is determined. The proposed model does not depend on any particular DFB structure, and hence can be applied to various DFB LD structures. Numerical results are presented for a three-phase-shift (3PS) DFB LD     

High-efficiency operation of phase-adjusted DFB laser by asymmetric structure

Differential efficiency has been increased by 50% in a phase-adjusted DFB laser by the introduction of an asymmetric structure. The problem of mode degeneracy in DFB lasers has been resolved without penalty on efficiency and output power.     

Improved selectivity and decreased spontaneous emission from anAR-HR coated SL-MQW DFB semiconductor laser amplifier

It is shown that the performance of a DFB filter/amplifier can be improved considerably with respect to selectivity and amplified spontaneous emission by applying a high reflective coating to the output facet. To illustrate this a strained-layer multiple quantum well DFB filter/amplifier with an output facet reflectivity of 97% is compared with a conventional, AR-coated phase adjusted DFB filter/amplifier. Peak fiber-to-fiber gains for these devices are 21 and 18 dB, respectively, when biased at 98% of their threshold current. The transmission gain of these DFB filter/amplifiers has been measured over a wavelength span of 30 nm. For the AR-HR coated SL-MQW DFB filter/amplifier the selectivity is improved with 11 dB resulting in an extinction ratio for interfering channels of better than 35 dB and the amplified spontaneous emission is reduced by 16 dB down to -37 dBm compared to the conventional DFB filter/amplifier     

Polarization-independent all-optical switching in a nonlinearGaInAsP-InP highmesa waveguide with a vertically etched Bragg reflector

We have theoretically designed and experimentally demonstrated polarization-independent all-optical switching in a nonlinear GaInAsP-InP highmesa distributed feedback (DFB) waveguide. The device, which is composed of a highmesa waveguide stripe and a vertically etched Bragg reflector, can be simply fabricated using one-step electron beam lithography and a reactive ion etching process. The device is suitable for integration with other photonic devices such as semiconductor optical amplifiers and wavelength converters. The structural birefringence of the device has a dependence on the waveguide parameters such as the refractive index and thickness of core and cladding. The structural birefringence was successfully eliminated by adjusting the width of the highmesa waveguide. The nonlinear vertical-groove DFB highmesa waveguide is attractive for a polarization-independent all-optical switch from the viewpoint of a large grating coupling coefficient, as compared with a grating-loaded DFB highmesa waveguide. The polarization dependence of the grating coupling coefficient has also been investigated experimentally. It is possible to obtain the polarization-independent grating coupling coefficient by adjusting the grating depth in the vertical-groove DFB highmesa waveguide, together with structural zero-birefringence of the device. Polarization-independent all-optical thresholding and bistable switching operations have been successfully demonstrated in the nonlinear vertical-groove DFB highmesa waveguide     

Tunable multiline distributed feedback dye laser based on the phenomenon of excitation energy transfer

Tunable multiline distributed feedback (DFB) lasing has been observed in the mixture of dyes rhodamine 6G (R6G) and cresyl violet (CV). The dye-pair is pumped by the two pairs of the pump beams derived from a common source at two different angles. A variation in DFB geometry up to seven orders suggests that the third order Bragg diffraction is suitable for such studies. A detailed study at high dye concentrations has been done by steady-state and ps time-resolved spectroscopy. The energy transfer phenomenon and the self-absorption mechanism both, are found to be responsible for the observed tunability and multiline lasing. The threshold energies required for the DFB lasing are also given here.     

A new method for the calculation of the emission spectrum of DFBand DBR lasers

A method based on transmission matrices that allows the emission spectra of arbitrarily complicated semiconductor laser structures to be computed below and above threshold has been developed. These can include active and passive periodic or uniform sections. As examples, the authors compute the emission spectra of a normal distributed feedback (DFB) laser, a DFB laser with a λ/4 phase shifter, and a surface-emitting distributed Bragg reflector (DFB) laser. To do that, Petermann's method for calculating the spontaneous emission coupling coefficient has been extended to the case of a periodic waveguide. It is shown how the spontaneous emission, when treated correctly, can be used to measure the coupling coefficient of the grating in a DFB laser with a λ/4 phase shifter     

Simple technique to improve the spectral quality of gain-switchedpulses from a DFB laser

The authors show that by coupling the output from a gain-switched DFB laser to a fibre loop mirror the spectral quality of the gain-switched pulse can be greatly improved. The SMSR of a gain-switched 1.5 μm DFB has been increased by 25 dB, and also the chirp has been reduced, by using this technique. This spectral improvement is vitally important in systems where the gain-switched pulses will pass an optical filter