Switchable mode-locking states in an all-fiber all-normal-dispersion ytterbium-doped laser

Multi-operation state in an all-normal-dispersion ytterbium-doped fiber laser is obtained by introducing nonlinear polarization or hybrid mode-locking mechanism in the laser cavity. In addition to operating the laser at continuous-wave mode-locking, various operation states including continuous-wave, Q-switched mode-locking, pulse-splitting, and harmonic mode-locking can be achieved by tuning the laser pump power or an intracavity polarization controller. Insertion of a semiconductor saturable absorber mirror in the cavity helps to shorten the output pulsewidth of the hybrid mode-locked laser. When the pump power is rapidly adjusted, a strong asymmetric hysteresis behavior can be observed during the manipulation between different orders of harmonic mode-locking.     

Characterization of the train-average time-frequency parameters inherent in the low-power picosecond optical pulses generated by the actively mode-locked semiconductor laser with an external single-mode fiber cavity

The specific approach to characterizing the train-average parameters of low-power picosecond optical pulses with the frequency chirp, arranged in high-repetition-frequency trains, in both time and frequency domains is elaborated for the important case when the semiconductor laser is matched by an external single-mode fiber cavity and operates in the active mode-locking regime. This approach involves the joint Wigner time-frequency distributions, which can be created for those pulses due to exploitation of a novel interferometric technique. Practically, the InGaAsP/InP-heterolaser generating at the wavelength 1320 nm was used during the experiments carried out and an opportunity of reconstructing the corresponding joint Wigner time-frequency distributions was successfully demonstrated.     

A 40-GHz Colliding Pulse Mode-Locked Semiconductor Laser

A monolithically active-passive integrated colliding pulse mode-locked semiconductor laser is demonstrated in the InGaAsP/InP material system.The device is mode locked at the second harmonic passive mode-locking regime with a wide mode-locking range.Pulse trains with the repetition rate of 40 GHz,3-dB rf line width of 25 kHz,the pulse width of 2.5ps,and a nearly transform-limited time-bandwidth product of 0.53 are obtained.     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

Threshold self-start of laser passive mode-locking under conditions of high-order frequency dispersion of the refractive index

The dependence of the self-start of laser passive mode-locking on the peak intensity of initial pulses under conditions of high-order frequency dispersion of the refractive index is analyzed using numerical simulation and analytical calculations. It is found that frequency dispersion of this type can lead to generation bistability. Specifically, laser passive mode-locking requires the generation of a sufficiently intense seed pulse in the initial noise distribution of the field in the laser cavity; otherwise, no laser passive mode-locking occurs and a steady-state lasing mode with the entire laser cavity filled with radiation is established in the system after the transient process is completed. The revealed threshold dependence of the self-start of laser passive mode-locking on the intensity of the initial seed pulse is one of the possible factors preventing the generation of ultrashort pulses in Kerr-lens lasers.     

注入噪声对光纤激光器锁模启动的影响

 从掺镱光纤激光器腔内的激光场出发,讨论了掺镱光纤激光器腔内的噪声信号对锁模启动的影响,并针对我们设计的8字腔超短脉冲光纤激光器进行了研究。通过对激光器腔内锁模过程的分析发现：在泵浦功率为214.75 mW时,自行研制的8字形腔掺Yb³⁺光纤激光器在未注入噪声信号时,输出端在30～50 s内获得稳定的锁模脉冲激光输出;在腔内注入脉宽30 ns,频率10 kHz,平均功率0.2 mW的脉冲噪声后,输出端在1~2 s内获得同样稳定的锁模脉冲激光输出。实验结果表明,注入激光器谐振腔内一定的噪声信号,可加速锁模的启动。     

关于被动锁模激光器涨落模型的补充说明

本文考虑了在被动锁模涨落模型中涨落脉冲集合中的脉冲数目对锁模的影响,并研究了激光器腔长对于锁模窗口和锁模阈值的影响。 关键词：     

Numerical analysis of pulse formation in solid-state lasers mode-locked with a linear external cavity

We analyse pulse formation in solid-state lasers mode-locked with a linear external cavity with translating mirror. Based on a numerical simulation the mode-locking mechanism is found to be that of an active mode-locking due to the explicitly time-dependent phase shift by the external cavity involving a slowly moving mirror and a non-zero temporal mismatch to the master cavity. Additional pulse shortening and stabilization is performed by the additive pulse mode-locking mechanism arising from self-phase modulation due to a Kerr-type non-resonant nonlinearity in the host crystal of the laser amplifier.     

半导体抽运Yb∶YAG 五镜腔KLM激光器理论分析计算

对半导体抽运的Yb∶YAG克尔透镜锁模激光器进行理论分析计算,分析五镜谐振腔和四镜谐振腔的稳区不同,利用稳区范围变化对五镜谐振腔稳定锁模机理做出合理解释.详细计算分析Yb∶YAG激光器内克尔调制效应对锁模的影响,获得最佳腔参量.在腔内没有插入硬光阑的情况下,利用五镜腔实现了Yb∶YAG晶体克尔透镜锁模运转.理论分析和实验结果相符.     

Single-walled carbon nanotubes on side polished fiber as a universal saturable absorber for various laser output states

We demonstrated four different laser operational states in the same passive fiber ring laser cavity by controlling solely the polarization state in a saturable absorber. The demonstrated laser operational states were continuous wave, mode-locking, Q-switching, and Q-switched mode-locking. The saturable absorber was fabricated by spin-coating a single-walled carbon nanotubes (SWCNT)/polymer composite on a side polished fiber providing enhanced nonlinear interaction with the SWCNT. The wide tuning range of the saturable absorber allows the simple means to generate different forms of laser output from a single laser cavity.     

Spectrum control and shaping of optical pulses in optical fibre interferometers

This paper discusses the use of single-mode fibre ring interferometers for injection laser line narrowing and for enhancement of optical emission power. The efficient launching into fibre ring interferometers of multi-frequency external cavity injection laser emission, in both the c.w. and mode-locking regime, has been achieved. Matching the optical lengths of the external cavity and fibre interferometer allowed the measurement of mode width of such a laser. A method is proposed for shaping optical pulses in fibre ring interferometers from constant intensity frequency modulated emission. The mode-locking regime of all-fibre external cavity injection lasers has been achieved.     

非腔长匹配相干叠加脉冲锁模激光器的实验研究

实现了一种新型的非腔长匹配相干叠加脉冲锁模Ｎｄ：ＹＡＧ激光器的锁模运转。锁模脉冲宽度为６０ｐｓ．给出该种新型锁模激光器的运转特性以及锁模状态与各种实验参数之间的关系。对于该种激光器的各种实验现象给出了简明清晰的物理解释。     

利用被动锁模技术实现超短脉冲激光输出实验

基于被动锁模技术,设计了结构紧凑的Z型谐振腔,采用半导体可饱和吸收镜作为被动锁模元件,利用激光二极管泵浦增益线宽较宽的Nd∶YVO4晶体,最终实现了连续锁模的脉冲输出.在输入功率为8.20W时,获得了输出功率为1.72W的1 064nm连续锁模脉冲激光输出,光-光转换效率达21%,锁模脉冲重复频率为110MHz.     

Stable mode-locking operation in a Cr:forsterite laser with a five-mirror cavity

The experimental finding of more-stable mode-locking operation in a five-mirror cavity than in a conventional four-mirror cavity for a Cr:forsterite laser [IEEE J. Quantum Electron. 33, 1975 (1997)] was interpreted by ABCD-matrix formalism. Since the optimum cavity configuration operation for mode-locking operation was attainable in the middle of the stable cavity condition, we conclude that one can easily achieve KLM alignment and stable mode locking with a five-mirror cavity.     

Cavity detuning effects in the synchronously mode-locked CW dye laser

A detailed numerical model analysis of the synchronously mode-locked CW dye laser is presented. In the analysis, good mode-locking is found mainly for negative cavity detuning. The calculated cavity length detunig effects are compared with the results of experiments performed on the Oxazine-1 dye laser. The agreement between theory and experiment is satisfactory. The experimental good mode-locking regime is predicted correctly by this analysis. The present calculations are also compared with the hitherto reported qualitative model analyses with a gaussian dye pulse approximation. The validity of these model analyses is examined.     

半导体可饱和吸收镜被动锁模侧面抽运Nd:YAG激光器研究

利用半导体可饱和吸收镜(SESAM)锁模技术实现的超快脉冲激光器具有结构简单紧凑、脉冲序列稳定等优势,在许多领域有着重要用途,自问世以来受到国内外的广泛关注.分析了SESAM被动锁模侧面抽运固体激光器的具体要求,进行了不同条件下的SESAM被动锁模侧面抽运Nd:YAG激光器实验.获得了最高平均功率9.5 W,脉冲重复频率71 MHz,单脉冲能量约141 nJ的皮秒激光脉冲.对SESAM被动锁模侧面抽运Nd:YAG激光器进行了实验和理论分析,对实现高功率连续超短脉冲激光器进行了探讨.     

输出近百纳焦耳脉冲能量的光子晶体光纤锁模激光器

设计并搭建了一种支持百纳焦耳量级的单脉冲能量输出的锁模光纤激光器.激光器基于σ型腔结构,采用掺Yb偏振型大模场面积光子晶体光纤作为增益介质,利用半导体可饱和吸收镜实现自启动锁模.激光器内没有色散补偿机理,使其工作在全正色散锁模状态.通过在谐振腔内引入多通长腔使激光器的重复频率降低至11.1 MHz,直接获得了平均功率为1.08 W,单脉冲能量为 97 nJ,脉冲宽度为4.17 ps的稳定锁模脉冲输出,经腔外色散补偿,脉冲宽度压缩至740 fs.     

The double and colliding pulse mode-locking (DCPM) of an Ar+ and dye laser in a ring cavity

We report the first double and colliding pulse mode-locking (DCPM) of an Ar⁺ and a dye laser in a ring cavity. An analytic solution for the stability of this ring cavity is presented, together with the experimental results on the DCPM laser.     

低阈值锁模状态可转换的全保偏光纤激光器

报道了一种可实现低阈值自启动的全保偏九字腔光纤激光器。谐振腔结构中使用相移器降低锁模阈值,当泵浦功率达到120 mW时,便可实现自启动的传统孤子锁模,中心波长为1530 nm,脉冲宽度为614.6 fs。随后泵浦功率逐渐增大到470 mW,实现了从孤子脉冲到类噪声脉冲的转换,在该锁模状态下的激光器输出功率为63.2 mW,对应的类噪声脉冲能量为5.69 nJ。所搭建的激光器具有低锁模阈值、自启动的优势,并且仅通过调节泵浦功率就能够实现超快脉冲和高能量脉冲间的转换,具有广泛的应用价值。     

低阈值掺钛蓝宝石激光器实验研究

结合特殊的谐振腔设计和半导体可饱和吸收镜，建成了一台低阈值的自启动掺钛宝石激光器 . 分别用3％和12％的输出耦合镜，获得了阈值低至390mW和600mW的稳定锁模脉冲输出. 采 用12％输出耦合镜，在12W抽运时，输出平均功率为114mW，对应的典型脉宽为17fs，谱宽 为47nm. 相对于以往的低阈值克尔透镜锁模激光器，锁模工作的范围区域加宽，减小了操作 难度，提高了稳定性. 关键词： 低阈值 半导体可饱和吸收镜 克尔透镜锁模 掺钛蓝宝石激光器