外光注入半导体激光器实现重复速率可调全光时钟分频

采用Fabry-Perot半导体激光器作为全光时钟分频器件,利用光注入半导体激光器产生的非线性动力学特性,实现了光脉冲的重复速率在9.0 GHz到19.8 GHz范围内连续可调的全光时钟分频. 同时利用半导体激光器速率方程,对脉冲光注入半导体激光器产生时钟分频进行了数值模拟. 实验和模拟结果表明半导体激光器在光注入的驱动下处于一周期振荡状态,当一周期振荡的二次谐波频率接近脉冲光的重复速率时,其二次谐波和基频被脉冲光同时锁定,此时将输出频率为脉冲光重复速率一半的时钟信号. 同时研究了波长失谐量和注入光功率对 关键词： 周期振荡 时钟分频 光注入 非线性动力学     

腔内相位调制全光纤脉冲激光器Ⅰ: 实验

报道了在低频直接相位调制下,掺铒光纤激光器的脉冲现象。在光纤激光器谐振腔中插入带尾纤的LiNbO3相位调制器,利用低频周期性信号进行相位调制,能够得到重复频率为几十千赫到几百千赫左右的均匀、稳定的脉冲光输出,且发现激光光谱变化等现象。分析表明,这种脉冲现象难以用调Q、锁模等传统的脉冲光理论进行有效地解释。简要讨论了脉冲光产生的物理机制,通过对相位调制与“驰豫振荡”关系的研究,唯象地认为相位调制和“驰豫振荡”是脉冲光产生的原因。     

腔内相位调制全光纤脉冲激光器Ⅱ: 理论

针对低频腔内直接相位调制时全光纤激光器的脉冲现象,提出了合理的理论解释。基于光纤激光器自脉冲和固体激光器空间耦合的理论,对脉冲光产生的机理进行了分析,解释脉冲光产生的物理机制。假定光纤激光器中存在两个正交的偏振态,且两个偏振态以固体激光器空间耦合的模型耦合; 在相位调制作用下,两个耦合的偏振态之间相位差变化,导致两个偏振态的耦合特性发生变化,从而产生脉冲光输出。建立相应的数学模型,进行定性的理论分析。数值模拟表明,理论分析与实验结果符合得很好。     

基于法布里-珀罗半导体激光器实现高重复频率光脉冲的时钟分频

实验研究了重复速率为6.32 GHz的光脉冲注人法布里-珀罗(Fabry-Perot)半导体激光器实现3.16 GHz光脉冲输出的时钟分频现象,讨论了 Fabry-Perot半导体激光器的偏置电流、注入光功率、注入光光谱以及光谱线宽等因素对时钟分频的影响.利用光注入半导体激光器产生的周期二振荡非线性动力学特性.实现了高重复速率光脉冲的时钟分频.研究表明,当注入光的光谱较窄且锁定Fabry-Perot半导体激光器某一纵模时,在较低的偏置电流和一定的注入光功率时,时钟分频才能发生.采用半导体激光器的速率方程.通过数值模拟,研究了半导体激光器的偏置电流和线宽增强因子以及注入光功率对时钟分频的影响,所得结果与实验结果相吻合.     

外光注入半导体激光器实现时钟分频

从理论和实验上研究了利用光注入半导体激光器对高重复速率光脉冲产生的周期振荡和时钟分频现象.结果表明，光注入半导体激光器引起的二倍周期振荡是使注入脉冲重复频率分频的直接原因.通过耦合速率方程，数值模拟了半导体激光器在外光注入时输出光的时间序列和功率谱，并且分析了激光腔内各种周期振荡的特征.研究表明，当注入光使半导体激光器出现稳定的二倍周期振荡，且注入光的重复频率为此振荡频率的二倍时，时钟分频即可产生实验中，采用重复频率为6.32GHz的光脉冲注入Fabry-Perot激光器，实现了3.16GHz时钟分频信号 关键词： 周期振荡 时钟分频 光谱侧带 光注入     

光脉冲注入下VCSEL的偏振开关特性

基于描述主、副垂直腔表面发射激光器（M-VCSEL,S-VCSEL）动态特性的速率方程,研究了M-VCSEL在脉冲电流调制下,输出光脉冲的偏振特性,以及S-VCSEL在M-VCSEL输出光脉冲的注入下,其偏振开关特性.研究结果表明：M-VCSEL在周期性脉冲电流的作用下,将产生周期性光脉冲输出;S-VCSEL在该光脉冲的注入下,输出光将在两个互相垂直的方向之间发生周期性转化,且变化周期与M-VCSEL所受到的调制脉冲电流周期相同;通过改变M-VCSEL驱动脉冲电流的调制幅度,可控制S-VCSEL输出的垂直偏振抑制比. 关键词： 垂直腔表面发射激光器（VCSEL） 光脉冲 偏振开关     

100W全光纤化高重频窄脉宽光纤激光器

报道了一种基于主振荡功率放大结构工作的全光纤化高重复频率窄脉冲宽度光纤激光器.种子源是一个直接电脉冲调制的1 063 nm光纤耦合输出半导体激光器.为了抑制放大器中产生的放大自发辐射光,将种子激光的脉冲波形调制为二阶超高斯型.峰值功率为950 mW的半导体激光器经过2级大模场掺镱双包层光纤放大器(纤芯分别为10μm和30μm)功率放大后,最终获得了平均功率为101 W、重复频率为200 kHz、脉冲宽度为14.77 ns、峰值功率为34.2 kW、3 dB光谱宽度为0.261 nm、光束质量M~2为1.17的脉冲激光输出.与传统的纳秒级脉冲光纤激光器相比,该激光器峰值功率高、光束质量优、光谱宽度窄、结构简单,可广泛应用于激光雷达、遥感探测、倍频和光参量震荡等领域.     

1GHz梳状波调制1.3μmDFB半导体激光器皮秒超短光脉冲产生的实验研究

本文介绍一种采用高重复率梳状波电流调制1.3μm分布反馈(DFB)半导体激光器产生皮秒超短光脉冲的技术。采用1GHz重复率尖脉冲电流直接调制1.3μm半导体激光器产生了最短15ps、输出平均功率为4.5mW的超短光脉冲。     

谐振式微光学陀螺不同调制方式下背向反射噪声分析

建立了基于反射式光波导环形谐振腔的谐振式微光学陀螺背向反射噪声分析模型,仿真分析了背向反射噪声强度项和干涉项在系统互易和非互易时的影响。比较了不同调制方式下,谐振式微光学陀螺系统中背向反射噪声的抑制情况,研究表明,分频调制下载波抑制的方式可将背向反射噪声抑制到极限灵敏度以下,同频调制下背向反射噪声受限于光开关/脉冲调制器的信道串扰。分别搭建了分频调制和同频调制系统,实验测试结果表明分频调制下陀螺输出稳定,同频调制下由于未对背向反射噪声强度项进行抑制,引入了10°/s量级的噪声,验证了理论仿真结果。     

脉冲幅度均匀化的有理谐波锁模光纤激光器

提出并实现了一种脉冲幅度可均匀化的有理谐波锁模光纤激光器。该激光器采用主动有理谐波锁模机制,可获得重复频率为整数倍调制频率的锁模脉冲信号。通过在光纤激光器谐振腔中添加非线性光纤放大环镜,并利用其反射率对输入信号强度的开关特性,实现对锁模脉冲信号的整幅。在1 GHz的调制频率下,分别获得了4 GHz和5 GHz重复频率的锁模脉冲信号输出,并且在一定的980 nm抽运功率下,可通过调节电光调制器的直流偏置电压大小以及调制信号的调制深度,使得脉冲幅度具有较好的均匀性。     

Multistage Fiber Amplifier with Spectral Compression Elements for High-Energy Laser Pulse Generation

We consider general principles of spectral compression of parabolic pulses in nonlinear optical fibers. It is known that the variance analysis provides a way to describe correctly the evolution of the pulse parameters under the spectral compression. We propose a computational model of multistage amplifier with spectral compression segments incorporated. The model provides the possibility to amplify middle-power input pulses to obtain pulse energies of hundreds of nanojoules with such output spectral characteristics that provide the possibility for further effective enhancement. We also discuss a modification of the model that provides the formation of a parabolic envelope and linear frequency modulation of the output pulse.     

基于耗散孤子种子的啁啾脉冲光纤放大系统输出特性

以不同滤波器带宽下获得的全正色散光纤激光器耗散孤子作为啁啾脉冲放大(CPA)系统的种子脉冲, 研究了光栅对和光纤展宽器CPA系统输出脉冲的可压缩性. 结果表明, 对于大能量耗散孤子种子脉冲, 当CPA系统采用正色散光纤展宽器时, 光纤群速色散与自相位调制之间的相互作用不仅可抑制耗散孤子脉冲光谱调制的影响, 还可使脉冲在光纤展宽器中自相似演化, 从而可提高CPA输出脉冲的可压缩性. 通过优化光纤展宽器长度, 对于耗散孤子种子源, 采用光纤展宽器的CPA系统输出脉冲可压缩性与主脉冲所占脉冲总能量之比均优于采用光栅对展宽器时的情况.     

啁啾脉冲堆积及其放大特性

 根据啁啾脉冲堆积的原理以及模型介绍了两路脉冲堆积时脉冲的时间与频谱特性,分析了堆积脉冲产生时间与频谱调制,以及交叠区产生非线性频率啁啾的原因。通过非线性薛定谔方程,分析了堆积脉冲的放大特性,介绍了啁啾参量对放大结果的影响以及放大后堆积脉冲的频率啁啾的变化。研究表明,在堆积脉冲的放大过程中自相位调制效应非常明显,严重影响了脉冲的频谱与频率啁啾。     

Simple and highly sensitive optical pulse-characterization method based on electro-optic spectral signal differentiation

A very simple self-referenced, linear pulse-characterization technique based on spectral phase reconstruction by frequency-domain signal differentiation is introduced. This technique can be implemented using electro-optic intensity modulation of the pulse under test with a synchronized RF sinusoid. The pulse spectral phase profile can be accurately and unambiguously reconstructed from only two measured energy spectra, i.e., at the input and at the output of the modulator, using a direct analytic equation. The method is experimentally demonstrated by precisely characterizing microwatt-power picosecond pulses after linear dispersion through short sections (50-700 m) of conventional single-mode fiber.     

High-rate pulse-train generation by phase-only filtering of an electrooptic frequency comb: Analysis and optimization

We investigate the generation of high-rate optical pulse trains by spectral phase-only filtering of a frequency comb derived from an electrooptically phase-modulated continuous-wave laser. The technique is initially analyzed as a two-step filtering process. First, a fundamental pulse-train with repetition-rate equal to the modulation frequency is obtained by line-by-line phase-cancellation of the electrooptic frequency comb. Second, the temporal Talbot-effect is considered so that the output pulse repetition-rate is an integer multiple of the electrooptic modulation frequency. Nonidealities found in the fundamental train lead, in general, to multiplied trains with important degradations. We numerically analyze optimum modulation conditions for generation of output pulse trains with minimum peak-to-peak variations and/or maximum extinction level. On the other hand, a genetic algorithm is considered to numerically find optimum line-by-line phase-only filters that generate output multiplied trains with minimized degradations. Numerical simulations show that, in general, this second approach allows for improvement in the quality of the resultant multiplied trains, in terms of the uniformity degree and/or noise-level, compared with the pulse trains resulting from the Talbot-effect-based approach.     

A comprehensive equivalent circuit model for the study of thermal and spectral characteristics in laser diodes

An improved electrical equivalent model for multimode laser diode incorporating thermal effects and spectral behavior is developed from the multi mode rate equations. The temperature dependent optical power, wavelength shift, spectral widths are determined in the dc sweep simulations. The output power, frequency chirp and temperature rise are evaluated under pulse modulation conditions. Further, the laser diode bandwidth dependence on temperature is also evaluated. Analysis is carried out in the temperature range of 283–343 K, by simulating the equivalent circuit, using PSpice circuit simulator.     

亚纳秒光脉冲抽运光子晶体光纤产生的瓦级超连续谱

研究了亚纳秒脉冲抽运光子晶体光纤产生高功率超连续谱的机理.采用掺镱锁模光纤激光器产生的脉宽570ps光脉冲,抽运1.8m光子晶体光纤,得到了平均功率为1.15W、光谱覆盖范围为750nm的超连续谱.通过实验和模拟结果的对比和分析,证实了亚纳秒脉冲抽运1.8m PCF产生超连续谱时,调制不稳定性效应起了重要作用.在研究了不同抽运功率下输出的超连续谱变化后,发现随着抽运功率的提高,输出功率也更高且超连续谱覆盖波段也更宽,在瓦级输出功率下依然未达到饱和展宽状态,还有进一步提高功率和展宽光谱的空间.     

Spectral-Phase-Modulated Cross-Polarized Wave for Chirped Pulse Amplifier with High Contrast Ratio

We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by wellcompressed spectral-phase fully-compensated fundamental laser pulses, the filter stretches the pulse bandwidth from 35 nm to 70 nm with a conversion efficiency of 20%. After implementing the filter into a femtosecond TW Ti:sapphire laser system, we generate 40 mJ output pulse energy with pulse duration of 18.9 fs. The temporal contrast of the compressed pulse is enhanced to 10~9.     

Combined self-phase modulation and amplification of femtosecond light pulses

The influence of depletable amplification, group velocity dispersion and self-phase modulation due to Kerr-type nonlinearity on pulse shaping in femtosecond pulse amplification has been calculated. With gain depletion which is typical for the last stage of multi-stage amplifiers, spectral broadening occurs which, under certain conditions, can be utilized for pulse compression. This spectral broadening as well as a predicted spectral shift is compared with experimental results.     

High-power, passively mode-locked Nd:GdVO₄ laser using single-walled carbon nanotubes as saturable absorber

We use a new (to our knowledge) fabrication method of a single-walled carbon nanotube (SWCNT) absorber without polymer to sustain high-power illumination. Using a series of saturable absorbers (SAs) incorporating different amounts of SWCNTs, we demonstrate mode-locking for a Nd:GdVO? laser in the 1 μm spectral range. Continuous-wave mode-locking (CWML) pulses with a maximum output power of 3.6 W at 1063 nm and high noise extinction of 61 dB has been achieved to give the highest pulse peak power of 3.6 kW and pulse energy of 30 nJ under 15 W pumping. To our knowledge, this is the highest CWML output power with SWCNT-SAs reported. The measured nonlinear absorption of the SWCNT-SAs shows a modulation depth of ~3% with subpicosecond recovery time.