掺钛蓝宝石激光器实现飞秒级自聚焦锁模运转

自1989年Goodbellt等人利用被动锁模方式第一次实现了掺钛蓝宝石激光锁模以来,人们利用多种锁模方式实现了掺钛蓝宝石激光器的锁模运转,其中特别引起广泛兴趣的是利用激活介质自聚焦效应实现掺钛蓝宝石激光器的自锁模,并于1991年达到了几十飞秒至几百飞秒的锁模运转,成为当今超快激光领域研究的前沿和热点.天津大学超快激光研究室经过几个月的研究于最近在我国首次实现了掺钛蓝宝石自聚焦锁模运转,脉冲宽度达到比184fs.     

自调Q自锁模固体激光器

利用被动锁模激光器的锁模原理,结合自锁模固体激光器中等效快可饱和吸收体的特性,讨论了控制运转状态的自锁模动力学方程和速率方程,给出了自调Q自锁模的条件,以及自调Q周期与激光器结构和运转参数的关系,所得结论与实验结果有很好的一致性。     

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.     

中红外超快光纤激光器研究进展

中红外波段覆盖重要的分子吸收区与多个大气透射窗口,该波段的超快激光器在多个领域具有广泛应用。基于光纤的中红外超快激光器近年来在激光发射与传输、超快脉冲产生与应用等方面发展迅速,为中红外波段超快激光开辟了新的研究手段与应用领域。综述了近十年来中红外超快光纤激光器的发展概况,介绍了近年来中红外波段的激光传输与增益手段。其中,重点回顾了近年来中红外超快脉冲产生技术的研究进展及其代表性工作,包括非线性偏振旋转、可饱和吸收体以及频移反馈锁模技术。此外,还介绍了中红外超快脉冲的压缩放大技术与超连续谱产生应用。最后讨论并总结了中红外超快光纤激光器面临的挑战与可能的发展方向。     

基于SESAM的Yb∶KYW飞秒激光器的研究

用激光二极管泵浦Yb∶KYW激光晶体,SESAM半导体可饱和吸收镜作为饱和吸收元件,实现了连续锁模的飞秒激光器的稳定运转.研究了全固态飞秒激光器的谐振腔设计、色散计算与补偿、SESAM调制深度和超快脉冲特性.使用锁模调制深度为0.8%,2.4%和3.0%的SESAM,实现了最窄脉宽为365fs,最高输出功率为253mW的锁模脉冲输出.     

利用啁啾脉冲光谱滤波和非线性偏振旋转技术实现高稳定性和开机自启动的全光纤掺Yb~(3+)光纤锁模激光器

建立理论模型,讨论了非线性偏振旋转全光纤锁模激光器的锁模过程、谐波过程以及导致激光器锁模运行难以稳定的影响因素.讨论了采用啁啾脉冲光谱滤波产生脉冲自振幅调制、增加激光器锁模稳定性和自启动能力的机理以及非线性偏振旋转与啁啾脉冲光谱滤波相结合实现锁模的物理过程和脉冲演化过程.研制出全光纤结构的超短脉冲掺Yb~(3+)光纤环形激光器,采用非线性偏振旋转和啁啾脉冲光谱滤波相结合的锁模技术,实现了激光器锁模的开机自启动和高稳定运行.对激光器进行了长期运行稳定性、锁模开机自启动能力、锁模输出参数可重复性监测.锁模脉冲中心波长1052.9 nm,谱宽9.1 nm,脉冲能量4.25 nJ,脉冲宽度17.8 ps.运行期间,各参数波动均小于0.3%.开机自启动能力和可重复性测试显示,激光器可实现一键自启动,启动后各参数可重复精度在0.55%以内.     

钛宝石飞秒激光器的锁模机理探讨

测量了X型折叠腔钛宝石飞秒激光器的发光动力学曲线，并运用传播圆 变换圆图解分析方法，系统地探讨了钛宝石飞秒激光器的自锁模机理和过程，提出了一种新的锁模机理——自脉动克尔透镜开关放大锁模. 关键词： 传播圆 变换圆 自脉动克尔透镜开关放大锁模 光学混沌     

高功率超快碟片激光技术研究进展(特邀)

自从碟片激光技术诞生以来,超快碟片激光器输出的激光功率和能量获得了显著提升,极大地促进了超快碟片激光器在基础科研、工业生产以及生物医学等领域的应用。本文对碟片激光技术的概念、锁模碟片振荡器以及超快碟片放大器进行了详细介绍,并对超快碟片激光器未来的发展和趋势进行了总结和展望。     

正色散激光器中的增益导引孤子

采用非线性薛定谔方程模拟了全正色散介质激光器中实现脉冲锁模输出的动态过程,理论表明,不同于工作于净色散为负的孤子锁模激光器以及腔内具有色散延迟线净色散为正的色散管理孤子和自相似脉冲锁模激光器,在纯正色散介质构成的锁模激光器中,增益饱和和增益窄化对形成稳定的锁模脉冲起重要的作用,在两者的作用下脉冲形成增益导引孤子.采用不同的锁模方式在纯正色散光纤锁模激光器中得到了稳定的增益导引孤子锁模,实验结果与理论模拟一致. 关键词： 锁模 正色散 增益导引孤子     

直接从钛宝石激光器获得超连续光谱

采用啁啾镜和棱镜对相结合补偿色散的方法在自调Q自锁模钛宝石激光器腔内直接产生了超 过一个倍频程的超连续光谱，光谱范围从460nm到1000nm；这是飞秒激光器输出光谱在短波 波段第一次突破500nm.这将使得脉冲的载波包络偏移频率的测量装置得到大大简化，同时也 提高了光频测量的稳定性. 关键词： 超连续光谱 啁啾镜 自调Q自锁模 钛宝石激光器     

Soliton dynamics in velocity matched ultrafast frequency conversion processes

We consider ultrafast second order frequency conversion processes, under group velocity matching conditions. The three wave interaction equations, describing velocity matched ultrafast optical frequency conversion processes, can be reduced to Sine-Gordon equation. In this way, the well known Sine-Gordon solitons can be mapped into three wave soliton solutions. Here, we report the numerical dynamics of three wave simultons, two-solitons and breathers in ultrafast second order frequency conversion processes.     

Regimes of operation states in passively mode-locked fiber soliton ring laser

The principal of passively mode-locked fiber soliton ring lasers is summarized, including its three output operation states: normal soliton, bound–solitons and noise-like pulse. The experimental results of the passively mode-locked fiber soliton ring lasers developed by us are given. Bound–solitons with different discrete separations and three-bound–solitons state have been observed in our fiber laser for the first time. The relationship among three operation states in fiber soliton laser is analyzed.     

孤子激光器及其发展

激光和孤子研究的进展,导致一种新型的、输出脉宽及形状可控的超短光脉冲激光器——孤子激光器的诞生。孤子激光器在光通讯、光计算、超高速现象的研究、超高速光电子器件的研制等方面有其独特的应用。它也使我们有可能对孤子效应本身进行深入研究。本文将叙述在单模光纤中形成孤子的机制,孤子激光及喇曼孤子激光原理,孤子及孤子激光研究的进展,包括孤子激光的稳定性、孤子自频移以及孤子间的相互作用力等。最后介绍一些已经出现的或将来可能出现的应用,并指出这是一个正在迅速发展的研究领域。     

2D noncarbon materials-based nonlinear optical devices for ultrafast photonics [Invited]

Ultrafast lasers play an important role in a variety of applications ranging from optical communications to medical diagnostics and industrial materials processing. Graphene and other two-dimensional(2D) noncarbon materials, including topological insulators(TIs), transition metal dichalcogenides(TMDCs), phosphorene, bismuthene, and antimonene, have witnessed a very fast development of both fundamental and practical aspects in ultrafast photonics since 2009. Their unique nonlinear optical properties enable them to be used as excellent saturable absorbers(SAs) that have fast responses and broadband operation, and can be easily integrated into lasers. Here, we catalog and review recent progress in the exploitation of these 2D noncarbon materials in this emerging field. The fabrication techniques, nonlinear optical properties, and device integration strategies of 2D noncarbon materials are first introduced with a comprehensive view. Then, various mode-locked/Q-switched lasers(e.g., fiber, solid-state, disk, and waveguide lasers) based on 2D noncarbon materials are reviewed. In addition, versatile soliton pulses generated from the mode-locked fiber lasers based on 2D noncarbon materials are also summarized. Finally, future challenges and perspectives of 2D materials-based lasers are addressed.     

Generation of bound solitons in actively phase modulation mode-locked fiber ring resonators

Bound solitons generated in actively mode-locked lasers enable new forms of pulse pairs and multiple pairs or groups of solitons in optical transmission or logics. In this paper, we present the generation of stable bound states of multiple solitons in an active mode-locked fiber laser using continuous phase modulation for wideband phase matching. Not only that dual-soliton bound states but also the triple- and quadruple-soliton pulses can be established. Simulation of the generated solitons are demonstrated. We have also prove by simulation that experimental relative phase difference and chirping caused by phase modulation of LiNbO₃ modulator in the fiber loop significantly influences the interaction between the solitons and hence their stability as they circulate in the anomalous path-averaged dispersion fiber loop.     

Short-pulsed Raman fiber laser and its dynamics

We provide a perspective review over the recent development of short-pulsed Raman fiber lasers(RFLs),which can provide laser emissions with flexible wavelengths for a variety of applications as well as an excellent platform to investigate various nonlinear pulse dynamics behaviors that cannot be captured in conventional rare-earth(RE)doped counterparts.Various pulse generation techniques have been explored in RFLs.However,the output pulse performance in terms of the pulse energy,duration and stability from short-pulsed RFLs is still inferior to their RE-doped counterparts despite significant advances made over the past few decades.Therefore,more efforts are required to improve these targets.In this review,we present a detailed overview of the short-pulsed RFLs based on different mechanisms from the principle to the experiment,including the Q-switching,gainswitching,mode-locking,synchronous pumping and other innovative techniques.In addition,Raman-induced pulse dynamics in ultrafast RFLs and RE-doped mode-locked fiber lasers(MLFLs)are briefly reviewed.Finally,a perspective outlook for the future ultrafast RFLs is provided based on their potential applications in industrial and scientific research areas.     

Passive harmonic mode locked all-normal-dispersion Yb-doped fibre lasers

Passive harmonic mode-locking of dissipative solitons is demonstrated in all-normal dispersion Yb-doped fibre lasers.A difference equation model of the mode-locked fibre lasers is adopted to simulate the intra-cavity nonlinear dynamics.Hysteresis phenomena around the mode-locking threshold,and the effect of introducing linear phase bias are discussed.The passive harmonic mode-locking as one kind of multipulsing operations is revealed.Moreover,the simulation shows the bistability between multipulsing and single-pulse or period multiplication.     

Dark solitons in mode-locked lasers

Dark soliton formation in mode-locked lasers is investigated by means of a power-energy saturation model that incorporates gain and filtering saturated with energy, and loss saturated with power. It is found that general initial conditions evolve (mode-lock) into dark solitons under appropriate requirements also met in experimental observations. The resulting pulses are essentially dark solitons of the unperturbed nonlinear Schr?dinger equation. Notably, the same framework also describes bright pulses in anomalous and normally dispersive lasers.     

超快X射线自由电子激光研究进展北大核心CSCD

现代光源的发展不断推动着人们从更深层次上理解物质的基本结构和动力学行为。X射线自由电子激光作为最先进的光源,其超高的峰值功率、超短的脉冲长度和优良的相干性,为人们以原子级时空分辨率探测和操控物质中的超快过程提供了可能。目前全世界已有多个X射线自由电子激光装置建成并投入使用,在原子分子物理、化学、生命科学、材料科学等各学科应用中都显示出了重要价值。同时大量的研究工作也集中于继续提高X射线自由电子激光的性能,包括把脉冲持续时间从fs量级进一步缩短至as量级,这将为超快科学的发展带来新突破。以超快脉冲产生为主线,综述了近年来超快X射线自由电子激光产生方案的研究进展,从产生原理、方案特性、最新成果等方面介绍了各类产生方案,总结对比了各方案的优缺点,最后对超快X射线自由电子激光的未来发展方向进行了展望。     

Period-doubling of gain-guided solitons in fiber lasers of large net normal dispersion

We report on the experimental observation and numerical simulations of period-doubling of gain-guided solitons in an erbium-doped fiber laser operating in the large net normal cavity dispersion regime. Features of the solitons before and after the period-doubling bifurcation are studied. Our results suggest again that period-doubling is an intrinsic feature of the mode-locked soliton lasers, which is independent of the mode-locked pulse property.