双端泵浦保偏光纤激光器

 以两台808 nm半导体激光器LD1和LD2为泵浦源,对光纤激光器双端泵浦进行了研究,获得了6.5 W的激光输出。实验分别测出了LD1和LD2半导体激光器单端泵浦和双端泵浦时的输出功率,对双端泵浦输出功率与单端泵浦功率之和进行了比较,利用双端泵浦提高了泵浦效率和输出激光功率。同时测量了输出激光的偏振度,通过计算得到双端泵浦输出激光的偏振度为0.5。     

Effect of steady-state conditions on self-pulsing characteristics of Yb-doped cw fiber lasers

Fiber laser resonator configurations have been analyzed theoretically on the basis of steady-state rate equations to optimize the laser conversion efficiency. Evolution of the pump- and signal powers and the saturated gain coefficient along the length of the laser medium has been simulated for high- and low-finesse resonators in forward- and backward pumping schemes. The corresponding fiber laser configurations have been setup to verify the results of simulation. Backward pumping configuration in an Yb-doped fiber laser has been found to be the most efficient, and in this configuration a maximum cw output power of 10.75 W in single transverse mode with an optical-to-optical conversion efficiency of 62.5% has been achieved. The laser output spectrum was peaked at 1093 nm with full-width at half-maximum (FWHM) line-width of about 9 nm. In the low-finesse resonator configuration, it has been found that experimental observations differ from theoretical simulation results. In this case, output power from both ends ceases to increase linearly beyond 1.8 W, and starts fluctuating due to the onset of strong random self-pulsing phenomenon. Our investigation shows that a non-uniform steady-state gain along the fiber length facilitates the self-pulsing process.     

Residual pump light as a probe of self-pulsing instability in an ytterbium-doped fiber laser

Self-pulsing instability in the ytterbium-doped fiber (YDF) laser is investigated with the pump-bypassed cavity configuration. The residual pump light acts as a probe of the intracavity dynamics, and the temporal behavior of the light shows correlations with the self-mode locking instability in the original cavity and the sustained self-pulsing instability in the modified cavity of the YDF laser. The results suggest that the interactions among stimulated emission, pump absorption and/or reabsorption could account for self-pulsing instability in the YDF laser. The pump-bypassed laser cavity configuration can be used to investigate the instabilities of various kinds of fiber lasers.     

Yb：Er共掺杂对掺铒光纤激光器中自脉冲行为的抑制作用

为了进一步提高镱铒共掺杂光纤激光器的实用性，对镱铒掺杂光纤激光器的自脉冲现象进行了理论分析。利用掺杂光纤中铒离子对的可饱和吸收的作用而引起自脉冲运转及离子对互作用模型作为理论基础建立系统模型，通过理论计算分析了共掺杂镱后掺铒光纤的有效抽运速率，证明了镱铒共掺杂可以提高有效抽运速率。使用这种光纤，可以使抑制光纤激光器中离子对导致的自脉冲效应所需的抽运功率水平大大降低。半导体激光器输出的抽运功率足以抑制由离子对导致的自脉冲，提供稳定激光运转。在研制稳定单频或高重复频率锁模光纤激光器方面，这种可用激光二极管抽运的镱铒共掺光纤具有很大的潜力。     

国产光纤实现同带抽运3000W激光输出

同带抽运是目前实现高功率光纤激光器的有效手段.本文基于同带抽运方式,以国产25/250μm掺镱双包层光纤为增益光纤,构建了全光纤化的主控振荡器功率放大器.实验中采用的国产光纤是中国电子科技集团公司第四十六研究所采用化学气相沉积结合气相-液相复合掺杂工艺制备的,其Yb~(3+)离子的分布更均匀,吸收截面更大,吸收系数更高.实验中,在种子光功率为67.8 W、抽运总功率为3511 W的条件下,实现了3079 W的激光输出,斜效率为85.9%,光束质量M~2约为2.14,3dB带宽为1.4nm,这是目前基于国产光纤同带抽运方式实现的最高功率.理论和实验结果表明国产光纤制备技术不断成熟,已经具备承受高功率输出的能力.继续提高抽运功率,优化增益光纤长度,改良散热方式,国产光纤有望实现更高功率的激光输出.     

Femtosecond oscillator on Yb:KYW crystal pumped by laser diode with fiber output

A femtosecond laser based on an Yb:KYW crystal with direct longitudinal pumping by a high-power semiconductor injection laser with a fiber output is described. Femtosecond pulses were generated in the self-longitudinal-mode-locking operating condition due to the use of a semiconductor saturable absorber. The average power of the oscillator was as high as 3.5 W at a central wavelength of 1035 nm, the pulse length and pulse repetition rate being 200 fs and 85.5 MHz, respectively. The product of the pulse length and the radiation spectrum width was 1.3 times higher than the theoretical limit for the pulse shape described by the function sech². The designed master oscillator can be also used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems.     

Nd:GdVO4 self-Raman laser using double-end polarised pumping at 880 nm for high power infrared and visible output

We report and evaluate a novel double-end polarised 880?nm pumping scheme for a Nd:GdVO₄ self-Raman laser, aimed at efficiently generating high output powers in the near-infrared and visible. Compared to conventional single-end pumping, this pump scheme has significant benefits in terms of absorption efficiency, temperature effects in the crystal, and mode-matching between the pumping beam and TEM₀₀ resonator mode. The maximum first-Stokes output powers were 4.1?W for CW operation and 5.63?W for quasi-CW (50?% duty-cycle) operation, with the diode-Stokes conversion efficiency of 11.2?% and 10.3?%, respectively. Visible emission was also realised by intra-cavity frequency-doubling (586.5?nm) or sum-frequency-generation (559?nm) using BBO or LBO crystals. For CW operation, the maximum output power was 3.46?W at 586.5?nm and 4.05?W at 559?nm, with diode-visible conversion efficiency of 10.7?% and 12.5?%; while for quasi-CW operation (50?% duty-cycle), the maximum output peak power was 6.5?W at 586.5?nm and 9.2?W at 559?nm, corresponding to 13.1?% and 18.9?% diode-visible conversion efficiency.     

Waveguiding effects in self-pulsing vertical-cavity surface-emitting lasers

Self-pulsing in semiconductor lasers containing a saturable absorber is well documented. We propose an alternative mechanism leading to self-pulsing in vertical-cavity surface-emitting lasers. We specifically consider waveguiding effects and determine the conditions for self-pulsing. Our theoretical and numerical results agree with experimental observations reported by Willemsen et al. [Appl. Phys. Lett. 77, 3514 (2000)].     

光纤回音壁模式激光产生长度的实验与理论研究

采用沿光纤轴向光抽运消逝场激励增益的方式,获得了沿光纤轴向较长范围的回音壁模式激光辐射.研究了这种激光器的激光产生长度与抽运能量间的关系.实验发现:当抽运能量刚超过激光产生阈值时,激光产生长度迅速增长;随抽运能量的继续增加,产生长度的增长趋势变缓;产生长度随抽运能量的变化关系决定于增益包层溶液的染料浓度和溶液折射率.根据抽运光沿光纤轴向以受抑全反射方式传播的物理特性,在抽运能量中引入了遵循比尔吸收定律的指数衰减函数,结合消逝场激励增益的回音壁模式激光理论,在分析系统增益和损耗的基础上由激光阈值条件推导出了 关键词： 回音壁模式 受抑全反射 消逝场 激光产生长度     

Self-pulsing in a double-clad ytterbium fiber laser induced by high scattering loss

The characteristics of self-pulsing behavior in a double-clad ytterbium-doped fiber laser are presented. The self-pulsing generates a supercontinuum spectrum that mostly propagates through the multimode structure of the fiber. In fact, 90% of the total power, including the fundamental laser wavelength and the generated supercontinuum spectrum, propagates trough the first cladding. The experimental evidence indicates that the main mechanism for the self-pulsing is the high scattering loss in the double-clad fiber.     

All-fiber tunable ytterbium-doped double-clad fiber ring laser

We have designed and realized a cw all-fiber tunable Yb-doped double-clad fiber laser in a unidirectional ring cavity. The side-pumping V-groove technique is used, yielding very good launching efficiency of the high-power pumping laser diode, together with a compact configuration. The fiber laser delivers as much as 800 mW of power and is tunable in the spectral range 1.04-1.10 microm . The laser linewidth is ~0.1 nm .     

Self-pulsing localized structures in a laser with saturable absorber

We consider a broad area heterostructured semiconductor laser with an integrated saturable absorber in a monolithic configuration. We extend beyond the single-longitudinal mode approximation a model already used to predict transversely localized structures or cavity solitons (CSs) in a shorter device and we numerically demonstrate the existence of self-pulsing transverse localized structures. Like CSs, these structures can simultaneously coexist in different transverse locations.     

Self-pulsing in Er3+-doped fibre laser

The output intensity of an erbium-doped fibre laser was studied. Experiments were performed with three pumping wavelengths: 514.5 nm, 810 nm and 980 nm. The laser output intensity exhibits three different dynamical behaviours: steady-state, sinusoidal variation or self-pulsing. In particular, in a bad (high-loss) cavity configuration, when the pumping ratio is increased above the lasing threshold the output intensity changes continuously from a steady-state to an infinite train of pulses. We also show that, depending on the cavity configuration, the transient oscillations display different forms.     

复合腔全光纤环形激光器单纵模双向同时激射的实验研究

提出并实验证实了三能级掺杂光纤复合腔环形激光器共振选模振荡原理和腔内自建可饱和吸收机制对双向行波共振谱的去耦作用，并实现复合腔掺Ｅｒ＾３＋全光纤环形激光器单纵蓦以向同时激射。     

高功率双包层光纤激光器抽运技术的方案分析

介绍了高功率光纤放大器双包层光纤的结构特点和双包层抽运的基本原理,在此基础上对高功率双包层光纤激光器的抽运关键技术作了分析,详细讨论了端面抽运技术、熔锥侧面抽运技术、内嵌反射镜抽运技术、角度抛光侧面抽运技术和V形槽侧面抽运技术等多种侧面抽运技术的结构及系统性能参数,并对各种侧面抽运技术的优缺点作了比较分析.研究结果表明,侧面抽运比端面抽运更有利于获得高功率激光输出,而在侧面抽运技术中则以V形槽侧面抽运技术为佳.     

LD泵浦掺铥(Tm3+)光纤激光器的数值分析

首先从掺铥光纤激光器的速率方程和光传输方程出发,建立数学模型,通过Matlab软件进行数值计算,分析了泵浦光和激光沿光纤的分布以及各能级离子数的变化.在不同掺杂浓度下,研究了小信号增益与入纤泵浦功率的关系以及泵浦光和激光功率与增益介质长度的关系.在不同泵浦功率下,研究了输出功率与输出耦合镜反射率的关系.进一步对不同泵浦吸收系数,研究了斜率效率和泵浦阈值与光纤长度的关系.分析结果表明存在最佳光纤长度和最佳耦合输出透过率,使得激光输出功率达到最佳值.     

芯泵浦高功率宽带谱平坦长波段光纤光源

为了获得高功率、宽带宽及谱平坦的长波段掺铒光纤光源,基于2级双程芯泵浦,应用偏振复用技术实现泵浦瓦级供给,在泵浦总功率和光纤总长度都不变的情况下,数值分析了4种光源结构的输出特性受泵浦和光纤分配比例的影响。结果表明,4种结构基本都能工作于L波段（1 565 nm~1 610 nm）,带宽受结构影响较小,但只有双程后向+双程后向结构可同时拥有高输出功率和高平坦度。其在总泵浦功率750 mW,第一级泵浦功率为300 mW,第二级泵浦功率为450 mW时,和光纤总长度21 m,第一级光纤长度为18 m,第二级光纤长度为3 m时,可实现输出功率314 mW,带宽32.41 nm,中心波长1 584.84 nm,平坦度2.23 dB的L波段超荧光光源。     

Visible cw-pumped supercontinuum

We report the experimental demonstration of a visible supercontinuum in the cw pumping regime. A 20 W ytterbium fiber laser at 1.06 microm is used to pump a photonic crystal fiber whose zero-dispersion wavelength decreases along the fiber length. Visible wavelengths are generated in the fundamental mode via trapping of dispersive waves by redshifted solitons.     

A 168-W high-power single-frequency amplifier in an all-fiber configuration

We present a high-power, single-frequency, narrow linewidth fiber amplifier based on master oscillator power amplification chains in an all-fiber configuration. The effect of the delivery fiber on the maximum output power is studied. A home-made 1064-nm seed laser with a 20-kHz linewidth is boosted to 129 W, and limited by stimulated Brillouin scattering (SBS) when the delivery fiber is 1.2 m long. By shortening the delivery fiber length to 0.7 m, the SBS threshold is increased efficiently and the maximum output power rises to 168 W with an 82.9% power conversion efficiency. The experimental results indicate that the output power can be further raised by shortening the delivery fiber length and increasing the pump power.