Generation and evolution of multiple operation states in passively mode-locked thulium-doped fiber laser by using a graphene-covered-microfiber

Using graphene-covered-microfiber （GCM） as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane （PDMS） to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.

A theoretical and experimental investigation of an in-band pumped gain-switched thulium-doped fiber laser

In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber （TDF） laser is investigated. The analytical formulations of pump energy threshold, peak power extraction efficiency, and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse. They are useful for understanding, designing, and optimizing the in-band pumped TDF lasers in a 1.9 μm-2.1 μm wavelength region. The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted, and our experimental results show good agreement with theoretical analysis.

Thulium fiber laser lithotripsy:Is it living up to the hype?

Objective:The holmium:yttrium-aluminium-garnet laser(Ho:YAG)has been the gold standard for laser lithotripsy over the last three decades.After demonstrating good in vitro efficacy,the thulium fiber laser(TFL)has been recently released in the market and the initial clinical results are encouraging.This article aims to review the main technology differences between the Ho:YAG laser and the TFL,discuss the initial clinical results with the TFL as well as the optimal settings for TFL lithotripsy.Methods:We reviewed the literature focusing on the technological aspects of the Ho:YAG laser and TFL as well as the results of in vitro and in vivo studies comparing both technologies.Results:In vitro studies show a technical superiority of TFL compared to the Ho:YAG laser and encouraging results have been demonstrated in clinical practice.However,as TFL is a new technology,limited studies are currently available,and the optimal settings for lithotripsy are not yet established.Conclusion:TFL has the potential to be an alternative to the Ho:YAG laser,but more reports are still needed to determine the optimal laser for lithotripsy of urinary tract stones when considering all parameters including effectiveness,safety,and costs.

Mode-Locked Thulium Ytterbium Co-Doped Fiber Laser with Graphene Oxide Paper Saturable Absorber

A mode-locked thulium ytterbium co-doped fiber laser （TYDFL） is proposed and demonstrated by using a commercial graphene oxide （GO） paper as saturable absorber （SA）. The GO paper is sandwiched between two fiber ferrules and incorporates a ring laser cavity to generate soliton pulse train operating at 1942.0nm at a threshold multimode pump power as low as 1.8 W. The mode-locked TYDFL has a repetition rate of 22.32 MHz and the calculated pulse width of 1.1 ns. Even though the SA has a low damage threshold, the easy fabrication of GO paper should promote its potentiM application in ultrafast photonics.

Analysis of gain distribution in cladding-pumped thulium-doped fiber laser and optical feedback inhibition problem in fiber-bulk laser system

The steady-state gain distribution in cladding pumped thulium-doped fiber laser（TDFL） is analytically and numerically solved based on the rate equations including loss coefficients and cross relaxation effect. With the gain curve, a problem, which is named optical feedback inhibition（OFI） and always occurs in tandem TDFL-Ho：YAG laser system, is analyzed quantitatively. The actual characteristics of output spectra and power basically prove the conclusion of theoretical analysis. Then a simple mirror-deflected L-shaped cavity is employed to restrain the external feedback and simplify the structure of fiber-bulk Ho：YAG laser. Finally, 25 W of 2097-nm laser power and 51.2% of optical-to-optical conversion efficiency are obtained, and the beam quality factor is less than 1.43 obtained by knife-edge method.

227-W output all-fiberized Tm-doped fiber laser at 1908 nm

In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.

2 μm超窄线宽光纤激光实现1 kW近衍射极限输出

2 μm波段光纤激光广泛应用于生物医学、环境监测、非线性频率转换,以及激光雷达和激光通信领域,备受研究人员关注。然而,该波段的激光器功率提升面临着低量子效率、高热负载和部分非线性效应的限制。基于反转概率调谐序列的高阶相位调制技术以抑制SBS效应、多级链路自动反馈的信号激光时域稳定控制技术以提升SRS阈值,以及光纤基横模纯化技术以控制光束质量,采用两级主放大结构,在1 950 nm波长实现了1 kW窄线宽近衍射极限输出,光光转换效率达55.6%,线宽3.8 GHz,光束质量M~2约1.2,在最高功率时无横向模式不稳定效应。

基于非线性偏振旋转效应的双波长可切换掺铥光纤激光器

提出并实现了一种基于重叠光纤光栅(Superimposed fiber Bragg grating,SI-FBG)和非线性偏振旋转效应(Nonlinear polarization rotation,NPR)的双波长掺铥光纤激光器(Thulium-doped fiber laser,TDFL)。两个SI-FBG作为波长选择器件,SI-FBG1的透射中心波长分别为1940.48 nm和1942.87 nm,SI-FBG2的透射中心波长分别为1940.47 nm和1942.83 nm。利用NPR效应抑制激光器谐振腔内的增益竞争,实现了稳定的单波长与双波长激射。实验测得可切换的单波长输出分别为1940.47 nm和1942.87 nm,光信噪比均高于37.1 dB,50 min内的波长漂移和功率波动均小于0.1 nm和0.67 dB。此外,通过调节谐振腔内的偏振控制器(Polariza⁃tion controller,PC)可以实现1940.47 nm和1942.87 nm两个波长同时输出,两波长光信噪比均大于15.3 dB,未在光谱仪监测过程中发现明显的波长变化,功率波动均小于0.63 dB。

2μm大能量掺铥脉冲光纤激光器研究进展

2μm波段掺铥脉冲光纤激光器目前可实现最高毫焦量级的能量输出,对医疗、材料、通信等领域有重要意义。本文主要介绍近年来大能量掺铥光纤激光器系统研究的主要进展,讨论大能量掺铥光纤激光器的技术类型和影响因素。在此基础上,对大能量掺铥光纤激光器的研究前景进行展望。

2μm激光消融技术在生物组织中的应用

激光因其能量集中、稳定性好、易于使用等优点,越来越多地被应用于生物医疗领域。近年来,2μm激光凭借着高水分子吸收系数的优势成为生物组织消融和碎石手术的理想选择,具有极大的应用前景。简要阐述了激光消融生物组织的光分布与光传热机制,介绍了2μm激光在体外组织、体内组织和碎石手术中的应用,总结了激光功率、工作模式、脉冲频率等对不同生物组织目标的影响,得出掺铥光纤激光器具有在激光消融领域替代掺钬钇铝石榴石(Ho:YAG)激光器潜力的结论。最后,讨论了掺铥光纤激光器在生物医疗领域发展的主要问题和趋势。

Gain-switched watt-level thulium-doped fiber laser and amplifier operating at 1.7μm

A 1.7μm gain-switched thulium-doped all-fiber laser with a master oscillator power amplifier(MOPA)configuration,utilizing a bandpass fiber filter and a 1550 nm erbium/ytterbium-codoped fiber MOPA,is demonstrated.The influences of pump pulse parameters(repetition rate and pulse duration)and laser cavity structures(ring and linear)on the laser performances were experimentally investigated.To the best of our knowledge,the power quenching and drop were observed in the 1.7μm gain-switched thulium-doped fiber lasers for the first time,resulting from the mode-locked-resembling operation and nonlinear effects.Moreover,the fiber ring-cavity laser was more stable than the linear-cavity laser in the time domain and power.Finally,a laser with a maximum average power of 1.687 W,a slope efficiency of 19.7%,a single-pulse energy of 16.87μJ,a pulse width of 425 ns,a repetition rate of 100 kHz and a peak power of 39.69 W was obtained.

掺铥光纤激光器设计与仿真

掺铥光纤激光器工作波段在人眼安全波段,凭借其结构紧凑、灵活性高、散热性强、光束质量好、量子效率高等优势得到了越来越多的关注。本研究设计1700~1800 nm波段的光纤激光器,将以泵浦光中心波长786 nm,去激发光纤激光器中心波长1740 nm。其中光纤长度设置为5 m。实验结果表明:泵浦光功率大于5 W时会产生激光,小于5 W时不会产生激光。通过实验可知,泵浦光功率会随光纤长度增长而减小,信号光功率会随光纤长度增大而增大。

S/S+ Band Tunable Thulium Doped Fiber Laser Anchored on 50 GHz ITU-T Grid

We demonstrate a S/S+ band tunable thulium doped fiber laser (TTDFL) anchored on 50GHz ITU-T Grid. Over 57nm of tuning range (1454.9 ~ 1512.0 nm) covering most of the Thulium bandwidth and more than 8dBm output power has been obtained with the pigtailed solid etalon filter and dual wavelength (1.5μm and 1.4μm) pumping.

基于非线性偏振旋转效应的多波长掺铥锁模光纤激光器

运用非线性偏振旋转效应实现了一种掺铥锁模多波长光纤激光器.采用环形腔结构,以1 565nm半导体光源为泵浦源,3m长掺铥光纤为增益介质.利用非线性偏振旋转效应进行滤波.当泵浦功率在800mW时,通过调节光纤偏振控制器,激光器出现了被动锁模状态的脉冲输出,脉冲重复频率为3.178MHz,脉冲宽度为617ps.进一步增加泵浦功率,激光器进入多波长输出的工作状态.调节偏振控制器在室温下得到1~5个稳定的波长激光输出,边摸抑制比为40~60dB.

高能量全光纤2μm掺铥脉冲光纤激光器

基于增益开关技术获得了稳定的高能量全光纤结构2μm脉冲光纤激光器,脉冲重复频率在10～50kHz之间可调,输出激光中心波长为1958nm,输出脉冲宽度随着泵浦功率的增加不断减小,其变化范围为1.2～1.7μs。采用两级掺铥光纤放大器对种子激光进行放大,当脉冲重复频率为10kHz时,获得了5.18W的输出平均功率,输出脉冲宽度为1.6μs,单脉冲能量为0.518mJ。

国产掺铥双包层光纤光谱特性研究

对内包层截面为六边形的国产掺Tm3+双包层光纤的光谱特性进行了较全面的实验研究。在1064nm激光泵浦下,观察到掺铥光纤发出明亮的蓝光,对其上转换谱进行了测量,并分析了产生的机理。在785nmLD泵浦下,测量了光纤的荧光谱。选用3种不同透过率的输出镜,对长度分别为4.5m和2.2m的掺Tm3+光纤实现了2μm波段的激光输出;利用红外光谱仪测得了激光波长。实验获得最大输出功率达到5.1W,斜率效率41.9%,并对实验结果做了分析。

掺铥(Tm^(3+))光纤激光器

根据基质分类和波长分类综述了掺铥光纤激光器的发展过程，并给出了我们关于掺铥石英光纤激光器研究中初步的实验结果。

10kW峰值功率高脉冲能量全光纤结构2μm掺铥光纤激光器

基于增益开关技术在高掺杂浓度掺铥光纤中获得了稳定的2μm种子脉冲激光,输出激光中心波长为1 979.4 nm,脉冲重复频率在1～100 kHz之间可调,输出脉冲宽度变化范围为60～200 ns.采用两级掺铥光纤放大器对该种子脉冲激光进行放大实验,当种子脉冲激光重复频率为20 kHz时获得最大输出平均功率为17.2W,输出光谱没有观察到明显的放大自发辐射噪声.最大功率输出时,脉冲宽度为82 ns,对应单脉冲能量为0.86 mJ,脉冲峰值功率高于10 kW.

主动调Q掺铥双包层光纤激光器

利用790 nm半导体激光器作为泵浦源、声光调制器作为Q开关,将4 m长掺铥双包层D型光纤作为增益光纤,在入纤功率9.17 W、调制频率50 kHz时,获得激光器最大输出功率为1.26 W.调制频率为30 kHz时,获得单脉冲能量40μJ的脉冲激光.激光器在30～50 kHz工作时可以获得稳定的脉冲输出.讨论了在阈值入纤功率附近形成1/2、1/3调制频率脉冲及在较大泵浦功率时形成多脉冲的原因.

2μm波段双波长间隔可调谐光纤激光器

提出并实验研究了一种2μm波段全光纤间隔可调双波长光纤激光器.该激光器采用传统的环形腔设计,以最大输出功率33dBm的1 565nm光纤激光器为泵浦源,4m单模掺铥光纤为增益介质,腔内为嵌入多模干涉滤波器的Sagnac环的复合滤波结构.该复合滤波器可实现间隔可调谐,高边模抑制比的双波长激光信号输出.通过泵浦功率的控制和对复合滤波器中偏振控制器的调节,实现双波长3nm到80nm间隔可调的激光输出,边模抑制比为60dB,线宽为0.2nm,功率稳定度为±1.5dB/h,双峰能量差小于4dB.