Competition of Rational Harmonic Mode-Locking and Continuous-Wave Lasing in Semiconductor Optical Amplifier Fiber Laser Under Optical Pulse Injection

Twentieth-order rational harmonic mode-locking (RHML) semiconductor optical amplifier fiber laser (SOAFL) pulses are demonstrated by using 1-GHz backward dark-optical comb injection. Maximum frequency detuning range of plusmn 300 Hz, broadened pulsewidth of 35 ps, and highest average power of 0.4 muW for twentieth-order RHML-SOAFL pulse are characterized. The extraordinary phenomena on the red-shifted wavelength from 1535.5 to 1541.5 nm and the corresponding spectral linewidth reduced from 12 to 3 nm are observed with the RHML order increasing to 8 or higher. Such a less pronounced RHML mechanism at higher orders occurred in the optically injection mode-locked SOAFL is mainly attributed to the weak mode-locking strength at high RHML orders as compared to continuous-wave lasing mechanism.     

Microstructure Fiber Soliton Laser

We demonstrate femtosecond pulse operation of a soliton fiber laser at 1.06-mum wavelength. This laser makes use of a single piece of microstructure fiber that has been designed to simultaneously provide anomalous dispersion and laser gain. Using a saturable absorber mirror with deep modulation depth to initiate and sustain mode-locking, this fiber provides clean and nearly transform-limited pulses down to a pulse duration of 180 fs. To the best of our knowledge, this constitutes the first demonstration of a pure soliton fiber laser in the neodymium gain band     

自动锁模光纤激光器研究进展

为解决基于非线性偏振旋转(NPR)的被动锁模光纤激光器(MLFL)抗环境干扰能力差和偏振难调等问题,基于不同算法和硬件的自动MLFL相继被提出并取得重大突破。其中,简单的遍历算法在自动锁模方案验证方面应用广泛,机器学习算法在仿真层面可以实现高效的自动锁模,最优化算法因其能进行高效的目标搜索而成为自动锁模的研究最热点。     

Laser Dynamics of a 10 GHz 0.55 ps Asynchronously Harmonic Modelocked Er-Doped Fiber Soliton Laser

Laser dynamics of a 10 GHz 0.55 ps asynchronously harmonic modelocked Er-doped fiber soliton laser are investigated both theoretically and experimentally. Theoretical analyses based on the master equation model solved by the variational method have indicated that all the pulse parameters of the laser output will exhibit complicated slow periodic variations in the asynchronous soliton modelocking (ASM) mode. New experimental methods based on analyzing directly the RF spectra of the ASM laser output have been developed to accurately determine the sinusoidal variation of the pulse timing and the pulse center wavelength for the first time. It is found that the pulse center wavelength variation can be as large as 1 nm half-peak-to-peak and the pulse timing variation can be as large as 3 ps. The consistency among all the experimental data and theoretical prediction is carefully examined and the results indicate that the ASM pulse dynamics observed experimentally are in good agreement with those obtained from the theoretical analyses.      

脉幅稳定的有理数谐波锁模光纤激光器

通过调节振幅调制器的静态偏压和驱动功率来控制调制器的驱动频率边频分量 ,在 2 5GHz的射频调制频率下 ,有效地抑制了 3～ 5阶有理数谐波锁模脉冲序列的幅度起伏 ,直接由激光器输出幅值稳定的有理数谐波锁模脉冲序列     

低重复频率全正色散脉冲光纤激光器的三种锁模状态

研究了一种基于半导体可饱和吸收镜（SESAM）锁模的线性腔掺镱光纤激光器,其工作在全正色散区域。实验中通过调节偏振控制器和抽运功率,观察到三种不同的锁模状态。除了相同的重复频率（基频435.6 kHz）,三种锁模状态的光谱、脉冲形状以及随抽运功率变化的演化过程均具有较大差异,其中状态一具有对称加宽的类高斯形光谱;状态二具有非对称加宽的平顶光谱;状态三的脉冲宽度随抽运功率增加急剧增大,脉冲特性类似于耗散孤子,但光谱与之不同。     

主动有理谐波锁模光纤激光器

利用有理谐波锁模,实现了锁模光纤激光器输出光脉冲重复频率的倍增,得到了重复频率10GHz~50GHz输出脉冲.     

同步抽运锁模的掺镱光纤激光器

同步抽运锁模是一种调制增益的锁模技术，就是调节抽运光的调制频率使之等于激光器纵模间隔的整数倍。通过对抽运光源半导体激光器的驱动电流进行正弦调制，实现了掺镱光纤激光器(YDFL)的同步抽运锁模。通过调整抽运激光器的调制频率，在相应于二次谐波锁模，4阶有理数谐波锁模条件下分别得到了较窄的脉冲输出。对重复频率625kHz的二次谐波锁模脉冲序列，脉冲宽度小于20ns，约为抽运光宽度的1／40；平均输出功率2．34mw，能量转换效率约为5％。     

Harmonic Passive Mode-Locking of a Single-Frequency Semiconductor Laser Submitted to Nonlinear Optical Feedback

We report on a theoretical analysis of the dynamical performance of a single-frequency semiconductor laser under the influence of nonlinear optical feedback. It is shown that the modal structure of such a laser is both dependent on the mirror characteristics and on the pump current. The analysis concentrates on the self pulsating regimes that can be observed, and more precisely on the occurrence of harmonic passive mode-locking. Generation of short pulses, characterized by a duration around 10 ps and a repetition rates as high as 20 GHz, have been demonstrated. The characteristics of this mode-locking strongly depend on the nonlinear mirror's temporal response     

主被动锁模光纤环形孤子激光器的研究

分析了一种新型的主被动锁模光纤环形孤子激光器．通过路径平均非线性薛定谔方程的求解．获得了激光器稳定运行的条件，并作了数值模拟，得到了工作波长为１．５５μｍ时．脉宽为９８５ｆｓ．谱宽为３２３ＧＨｚ．重复频率为１０ＧＨｚ的双曲正割变换限制孤子脉冲序列。     

主动锁模光纤激光器有理数谐波锁模与重复频率的分频现象

在主动光纤锁模激光器的实验中,我们在较低的调制频率下观察到了有理数谐波锁模的现象。利用不到１．４ＧＨｚ的调制信号,得到了２．８－５．６ＧＨｚ的光脉冲信号。此外,还观察到了重复频率的二分频现象;即输出的光脉冲的重复频率是调制频率的１／２。     

调Q及连续掺Yb光纤激光器中的自锁模研究

在用半导体激光器抽运的单包层掺Yb调Q光纤激光器中观察到了清晰稳定的自锁模脉冲序列。脉冲包络形状为调Q脉冲。每个锁模脉冲的幅值由其在调Q脉冲中的相应位置决定。经过分析，认为自相位调制是调Q光纤激光器中产生锁模的主要原因。自相位调制的存在使得光脉冲的频谱被展宽，当这种展宽和腔的模式间隔相差不多时，腔内的模式便能相互作用，直到它们之间产生一个固定的相位关系。也即形成锁模。在此基础上。去掉声光晶体，并用两个光栅作为腔镜，实现了全光纤法布里-珀罗(F-P)腔锁模光纤激光器。改变腔结构，分别采用光栅和光纤反射圈作为前后腔镜，同样观察到了锁模脉冲。经过观察发现，锁模脉冲的产生和掺Yb光纤的浓度、长度、抽运功率的大小有着密切的关系。这为锁模脉冲的产生提供了一种新的方法。     

间距可控的耗散孤子分子锁模光纤激光器

通过在耗散孤子锁模光纤激光器外接入马赫增德尔干涉仪,实现了间隔可控的耗散孤子分子超短脉冲输出.马赫-曾德尔干涉仪由两个50∶50分束器和一个可调谐时间延迟线构成.通过调节时间延迟线控制马赫-曾德尔干涉仪两臂的光程差,可以实现耗散孤子分子的间距连续可调谐.实验中实现了脉冲间隔分别为0.8、1.3、2.37、4.25、6.24、9.4、15.3 ps的耗散孤子分子,对应的光谱调制间隔分别为8.3、6.1、3.83、1.88、1.27、0.85、0.52 nm.理论分析了孤子分子的产生机理并与实验数据保持一致.本研究为实现间距可控孤子分子超短脉冲提供了一个行之有效的方法.     

Soliton Thulium-Doped Fiber Laser With Carbon Nanotube Saturable Absorber

We report stabilization of a thulium-holmium codoped fiber soliton laser with a saturable absorber based on carbon nanotubes. The laser generates transform-limited 750-fs pulses with 0.5-nJ energy.     

光纤激光器中锁模孤子序列的长周期脉动

实验观察到非线性偏振旋转锁模光纤激光器中锁模孤子及孤子簇的长周期脉动现象.单孤子与孤子簇的脉动周期达103和102次脉冲周期量级.脉动周期及脉动包络形状与抽运功率及腔内偏振设置有关.孤子脉冲的长周期脉动现象归因于不严格的1阶偏振态设置.不严格的1阶偏振态设置使得偏振相关隔离器对每次腔内循环的锁模孤子脉冲进行了微弱的周期偏振滤波.积累的偏振滤波损耗导致了锁模脉冲序列出现长周期脉动.     

利用光纤环激光器和色散搭配的孤子传输

对不同波长的光脉冲在由正负色散光纤的组成的光纤链中的传输特性进行了数值和实验研究。实验结果和数值分析表明，在相同的初始条件下，短距离传输时，采用平均色散为正常色散的光纤传输要优于孤子传输方式，长距离传输时，采用孤子传输要优于脉冲在平均色散为正常色散的非线性光纤中传输。在正负色散位移的光纤链中的孤子传输，有一最佳波长。     

Novel Analytic Theory for Laser Mode-Locking

The time-domain ABCD matrix formalism is based on the propagation of a Gaussian pulse which is characterized by the pulsewidth and chirp. In this paper, we will perfect this method and derive time-domain ABCD matrices for more optical devices. Especially, we extend this perfected theory to analyze the principle of passive mode-locking by reasonable approximation though, as we know, the output pulse generated from passive mode-locking fiber laser is of sech-shape. It is attractive because it can present a fairly apparent view to understand the mechanism of fiber lasers as well as analytic results to understand the pulse characteristics.     

非线性偏振旋转光纤环形孤子激光器的分析

详细分析了非线性偏振旋转被动锁模光纤环形孤子激光器的自起动过程、孤子脉宽及稳定性与各激光参数的关系.通过孤子参量演化方程的求解.获得了激光器稳定运行后脉宽的解析表达式以及激光器的稳定运行条件.     

光纤孤子激光器及用其作源的光孤子传输实验

介绍了一个１．５５μｍ光纤孤子激光器及利用它作源的光孤子脉冲传输实验。其中采用了掺铒光纤放大器锁模技术．实测孤子激光器输出脉冲宽度为３０ｐｓ．谱宽为０．１６ｎｍ；经过５０ｋｍ色散位移光纤传输后，其脉宽与谱宽基本维持不变．     

Tunable Raman Soliton Source Using Mode-Locked Tm–Ho Fiber Laser

We report a femtosecond pulse source that uses a mode-locked Tm-Ho oscillator and a self-frequency shift of Raman solitons in Tm-Ho power amplifier. The master oscillator mode-locked by an antimonide-based saturable absorber mirror produces 750-fs transform-limited soliton pulses over the tuning range from 1912 to 1972 nm. The soliton self-frequency shift in the amplifier resulted in transform-limited pulses with the wavelength adjusted by varying the amplifier pump power. We obtain ~150-fs soliton pulses at the wavelength of 2150 nm with average power up to 230 mW corresponding to the peak power of 27 kW. The efficiency of Raman conversion ranges from 47% to 62% over the tuning range