超短脉冲新技术的实验与展望

八十年代碰撞脉冲锁模(CPM)与单模光纤压缩脉宽新技术的产生,使超短激光脉冲趋于毫微微秒的量级。国内在碰撞脉冲锁模技术的运用研究中取得了显著效果。本文提供了碰撞脉冲锁模实验研究与压缩脉宽最新进展之信息。     

双波长可切换方波类噪声锁模线形光纤激光器

采用非线性偏振旋转锁模技术,在线形腔光纤激光器获得双波长可切换方波类噪声锁模。通过调节腔参数,激光器在波长1530 nm和1563 nm处分别获得可切换单波长方波类噪声锁模,最大脉冲宽度分别为12 ns和26 ns,腔内最大的脉冲能量分别可达14.7 nJ和45.6 nJ。此外激光器还可在这两波长处实现双波长类噪声锁模,锁模脉冲呈阶梯形,最大脉宽为5 ns,阶梯形脉冲的产生主要源于不同中心波长处的方波脉冲叠加。实验结果有助于进一步理解线形腔光纤激光器中方波类噪声的产生机理和特性,并为多波长高能量光源的设计提供参考。     

染料碰撞脉冲锁模的理论研究

提出染料碰撞脉冲锁模新理论,它的物理图象清晰,能较好地说明锁模脉冲的性质,特别在频率方面。     

利用非线性偏振旋转锁模技术产生0.7nJ,1.5ps光脉冲

为了研究锁模光纤激光器以增益平坦型掺铒光纤放大器作为增益介质对输出特性的影响,采用增益平坦型掺铒光纤放大器结合光纤偏振控制器、偏振相关光隔离器组成锁模光纤激光器,基于非线性偏振旋转锁模技术,实现稳定、自起振锁模运转,得到了中心波长1560nm、重复频率6.495MHz、单脉冲能量0.7nJ、脉宽1.5ps的超短光脉冲。同时实验观察到峰值波长为1557nm和1570nm的双峰值波长锁模脉冲的产生。结果表明,采用增益平坦型掺铒光纤放大器替代普通掺铒光纤组成锁模光纤激光器,可获得较高单脉冲能量的超短光脉冲,锁模脉冲的输出光谱可能出现双峰结构,从而可为超短脉冲光纤激光器设计及实用化提供参考。     

被动锁模光纤激光器中双波长脉冲的产生

报道了从一个典型的基于非线性偏振旋转被动锁模光纤激光器中产生双波长锁模脉冲的研究。双折射诱导的波长相关腔传输使得激光器能同时在2个或多个波长上振荡,本文设计的激光器中最多有3个波长同时产生。由于偏振相关隔离器(PDI)引入的另外偏振相关腔损,通过调节偏振控制器(PC),3个波长中的任意2个能同时共振,并同时锁模。此外,双波长脉冲中2个不同波长的脉冲会相互作用,并通过交叉相位调制形成各种各样的调制格式。     

波长可调谐被动锁模光纤激光器

为在光纤激光器中获得特定中心波长的锁模激光,进行了采用非线性光纤环形镜锁模的掺Yb3+光纤激光器的波长可调谐实验研究。获得了自启动锁模、中心波长在1030nm~1081nm范围内连续调谐的锁模脉冲输出;在中心波长1053nm时,测得光谱带宽6nm、脉冲宽度234.375ps、输出功率2.05mW、重复频率3.842MHz。这种被动锁模光纤激光器的锁模过程可以完全自启动,几乎不受外界环境变化的影响,可以长时间稳定工作,不仅可以提供特定中心波长的锁模激光,而且有望成为其它科学研究工作的中心波长可调谐的宽带锁模光纤激光种子源。     

测量飞秒激光脉冲的实时扫描相关器

近几年，超短光脉冲研究进展非常迅速，特别是碰撞脉冲锁模环形染料激光器的出现，使光脉冲进     

固体激光器的碰撞锁模的涨落理论和统计特性

利用涨落模型,对固体激光器的碰撞锁模脉冲的脉宽、能量及其稳定性进行理论分析,唯象地引入粒子数“光栅”,使用计算机进行模拟计算。结果表明:碰撞锁模的锁模值较尖锐(仅高于激光阈值2％)。在通常可达到的运行条件下,碰撞锁模脉     

锁模光纤激光器中偏振相关输出特性的实验研究

实验观察到非线性偏振旋转锁模光纤激光器输出的偏振相关的多波长输出现象、脉冲频谱边带及其抑制现象,以及多重偏振态导致的脉冲序列峰值调制现象.分析了这些与偏振相关的输出特性的物理成因,指出多波长锁模脉冲输出现象源于激光器中器件的保偏尾纤提供了多个偏振光程;锁模脉冲频谱边带现象源于由色散波同锁模脉冲内与其偏振态相同的脉冲内部成分干涉的结果,通过调整激光偏振态使锁模脉冲演化成矢量孤子就可消除频谱边带问题;时域脉冲序列的峰值调制现象源于激光器中偏振片周期偏振调制导致的矢量孤子多重偏振态.     

碰撞脉冲锁模Nd~(3+):YAG激光器

本文报导碰撞脉冲锁模Nd~(3+):YAG激光器的实验研究。输出脉宽10～12ps,单序列锁模脉冲再现性～100％,峰值功率>50MW。     

Single and double mode-locked ring dye lasers--Theory and experiment

A computer model is made of the colliding-pulse ring dye laser for mode-locked production of short pulses. Initial conditions of either noise or a small CW oscillation eventually result in the same final solution. Resolution is 10 ps in the model, and a digital filter represents dispersion. A gain-sharing long pulse mode often results, but large effective absorption cross section in the mode-locking dye and optimum separation of the two dyes (one quarter of the total resonator length) favor the desired short pulse formation. The model does not include the transient grating effect. Experiments with a ring laser using rhodamine 6G and DODCI confirmed the parameters important to the two regions. Double mode locking, in which the mode-locking dye also lases, was also studied both in the model and experimentally. It is not yet clear if the advantages of colliding pulse mode locking apply to double mode locking.     

A physical model for mode-locking process of colliding pulsemode-locked multiquantum-well semiconductor laser

In this paper, we first present a physical model for mode-locking process of the colliding pulse mode-locked multiquantum-well laser diode (CPM-MQW-LD). The absorption of saturable absorber on pulse leading edge and the scattering of the transient grating generated in absorption and gain regions on pulse trailing edge are considered. As an example, the mode-locking process of a multiquantum-well structure laser and the effect of transient grating on pulse width and peak power are studied     

Dynamics of monolithic passively mode-locked semiconductor lasers

Monolithic colliding pulse mode-locking (CPM) in semiconductor lasers is compared with self colliding pulse mode-locking (SCPM) through a large signal dynamic computer model which incorporates most of the significant features of semiconductor lasers. These include gain saturation, spontaneous emission, the gain-frequency relation, and the line-width enhancement factor. This new model replicates many of the published experimental results and also gives additional insight into the internal operation of the device. In particular, gain saturation combined with the standing waves created by colliding pulses within the saturable absorber produce a transient gain grating. This is found to have significant effects in locking either the even or the odd modes together in CPM. A performance comparison between CPM and SCPM is completed and some key design parameters of both configurations are explored     

Intracavity pulse compression in a laser with nonlinear resonator

Using a computer simulation, the authors have studied self-start of passive mode-locking in a laser with a nonlinear mirror in the form of a fiber loop reflector. They have demonstrated that intracavity interferometric pulse compression in a nonlinear resonator makes it possible to broaden the bandwidth and to accomplish efficient pulse shortening. Stable solutions have been found for perfect mode-locking with a steady-state pulse bandwidth which essentially exceeds the gain bandwidth     

掺铬镁橄榄石作为1.06μm激光可饱和吸收体的研究

采用Cr4 :Mg2SiO4作为可饱和吸收体,实现脉冲式平凸非稳腔Nd:YAG激光器的被动调Q运转,得到脉宽34ns、输出能量13.8mJ的激光脉冲。在合适的实验条件下,也观察到被动锁模现象。实验上比较了激光器的不同腔结构和参数对调Q激光脉冲宽度和能量的影响,并给予合理的理论解释。     

Synchronized transform-limited operation of 10-GHz colliding pulse mode-locked laser

We report a 10-GHz colliding pulse mode-locked laser fabricated with integrated active-passive waveguides. The laser fabrication adopted a deep reactive ion etching and single-step metal-organic vapor phase epitaxy regrowth process for forming the buried heterostructure waveguide. Clean output pulses resulted from laterally tilting the active-passive interface and effectively suppressing residual back-reflections at the interface. Hybrid mode-locking resulted in a synchronized transform-limited sech/sup 2/optical waveform. Pulsewidth, chirp, timing jitter, and frequency-locking range were investigated through systematic device biasing condition optimization.     

Time-domain ABCD matrix formalism for laser mode-locking andoptical pulse transmission

ABCD matrix formalism in the time domain has been newly developed on the basis of laser beam and resonator analyses which were developed under a Gaussian paraxial approximation. We derive matrix elements for amplitude and frequency modulations, group velocity dispersion, optical bandpass filter dispersion, and lumped self-phase modulation under a parabolic approximation. Applications to AM, FM, and stretched-pulse laser mode-locking are described by using these time-domain matrices. An application to pulse transmission in a dispersion-allocated system is also described     

双掺(Ce~(3+)、Nd~(3+)):YAG晶体对撞脉冲锁模的研究

一、引 言 新晶体双掺(Ce~(3+)、Nd~(3+)):YAG是一种具有高转换效率的激光增益介质~[1],它利用Ce~(3+)、Nd~(3+)的敏化途径提高激光效率。晶体中的Ce~(3+)离予通过辐射和非辐射二种方式向Nd~（3+）转     

Picosecond photonics

The basic principles of new ultrafast all-optical processing devices are experimentally demonstrated. One type of device relies on the interaction between an input signal and two colliding spatial solitons of a different wavelength in a planar waveguide with third order nonlinearity. The devices which belong to the second type are based on second order nonlinear interactions (degenerate difference frequency mixing) and operate as ultrafast sampling gate or as deflector or as phase conjugator. We report in a second part the design and performances of a laser that could be used to trigger the above mentionned systems. The laser cavity has two arms and two separate diode-pumped laser crystals (Nd/YAG). The two laser beams are coherently recombined inside the resonator into a single Gaussian beam. Picosecond pulses emission is ensured by passive mode-locking thanks to a nonlinear mirror set-up.     

Theory for passive mode-locking in semiconductor laser structuresincluding the effects of self-phase modulation, dispersion, and pulsecollisions

We present a theory for passive mode-locking in semiconductor laser structures using a semiconductor laser amplifier and absorber. The mode-locking system is described in terms of the different elements in the semiconductor laser structure. We derive mode-locking conditions and show how other mode-locking parameters, like pulse width and pulse energy, are determined by the mode-locking system. System parameters, like bandwidth, dispersion, and self-phase modulation are shown to play an important role in mode-locking conditions and results. We also discuss the effects of pulse collisions and positions of the mode-locking elements inside the cavity on mode-locking stability and show that these effects can be easily included in the presented model. Finally, we give a number of design rules and recommendations for fabricating passively mode-locked lasers