Dependence of ion-pair induced self-pulsing in Er-doped fiber lasers on emission to absorption ratio

We show theoretically that the ion-pair induced self-pulsing in Er-doped fiber lasers depends largely on the ratio of emission to absorption cross sections, and can be significantly suppressed as this ratio is increased. Our experimental results agree qualitatively with this prediction. This result is important for stabilizing Er-doped fiber lasers where short-cavities and high-gain fibers are required.     

三波长环形腔掺铒光纤激光器的设计

设计了一种结构简单、成本低的TW-EDFL(三波长掺铒光纤激光器),其输出波长分别为1 530、1 540和1 550nm,实现了1.5mW的稳定输出功率。研究了EDF(掺铒光纤)长度和泵浦功率与输出功率的关系,得到最佳EDF长度为4.15m、最佳泵浦功率为200mW的结论。在结构中加入3个VOA(可变光衰减器),运用增益均衡的方法来平衡谐振腔内3路信号光的增益和损耗,避免了EDF在室温下的模式竞争效应。     

基于SESAM的被动调Q光纤光栅掺铒光纤激光器

提出并研究了一种线性腔结构的基于 SESAM(半导体可饱和吸收镜)的被动调 Q光纤光栅掺铒光纤激光器,该激光器无需采用偏振控制器控制激光偏振态,简化了调 Q 激光器的结构。该激光器的中心波长为1549.975 nm,阈值功率为143 mW,斜效率为1.2%。当泵浦功率从149 mW增加到180 mW时,脉冲重复频率从5.431 kHz增加到9.778 kHz。当泵浦功率为155 mW时,激光脉冲的能量为5.6 nJ,重复频率为6.538 kHz,脉冲宽度为40μs。     

单模掺铒光纤激光器极限输出功率的数值研究

通过对掺铒光纤激光器极限输出功率的受限因素分析,在考虑非线性效应、热效应、光损伤等因素的情况下,结合掺铒光纤激光器的单模条件,计算得到单模掺铒光纤激光在1 570 nm 工作波段下的极限功率为6.34kW。同时计算了在少模条件下掺铒光纤激光器的极限输出功率为53.39 kW。还分析了单频情况下掺铒光纤激光器的极限输出功率,结果表明:在绝对单频的条件下,掺铒光纤激光器的极限输出功率为245W。并重点对实际中可行的提升输出极限功率的改善方法进行了分析,结果表明:降低纤芯数值孔径以及提升少模光束运转下的光束质量是提升单模条件下掺铒光纤激光器极限输出功率的重要手段。     

Analysis of Er-doped fiber laser stability by suppressing relaxation oscillation

For Er-doped fiber lasers, we show that the fluctuation of lasing power caused by resonant pump-power perturbations is inversely proportional to the lifetime of photon in the laser cavity. Analysis shows that Er-doped fibers with high-gain coefficient are favorable for fiber lasers in the view of point of suppressing the lasing-power instability caused by the resonant pump perturbation. The results obtained are especially useful for single-frequency Er-doped fiber lasers which have a very short cavity length, i.e., a short lifetime of photon in the cavity.     

Polarization-maintaining fiber Bragg gratings for wavelengthselection in actively mode-locked Er-doped fiber lasers

Fiber Bragg gratings written in polarization-maintaining fiber are proposed for wavelength selection in actively mode-locked Er-doped fiber lasers. Combined with single-polarization optical circulator, they form unidirectional transmission filters that can be incorporated in polarization-maintaining laser cavities. We have fabricated such a grating in hydrogen-loaded PANDA fiber and we have incorporated it in a polarization-maintaining actively mode-locked Er-doped fiber laser designed to generate soliton-like pulses. Dependencies of pulse duration and spectral width on average intracavity power were measured. The power range over which soliton-like pulses were generated without pedestals was found to be ultimately limited by the grating's bandwidth     

双包层掺铒光纤激光器的数值模拟与实验

对双包层掺铒光纤激光器进行理论上的数值模拟和实验研究.根据数值模拟计算,选择2.5m双包层掺铒光纤,利用包层抽运技术,采用大功率半导体激光器作为抽运源,在入纤抽运功率为4.5W时,获得功率670mW的1.56μm激光输出.     

Clad-pumped Yb,Er codoped fiber lasers

Double-clad and Yb,Er codoped fiber lasers emitting at eye-safe wavelengths (>1.5 μm) have been investigated by varying the codopant concentrations, core modifiers, fiber length, and the spectrum of the diode pump. With a proper composition, the laser output contains only one lasing wavelength, at 1.6 μm. Highest slope efficiency greater than 60% for this three-level system, emitting only at 1.6 μm, has been obtained by using a 20-m-long, double-clad and codoped fiber with the core and clad diameters of 6.3 and 300 μm, respectively. By tradeoff of slope efficiency fur higher output power, a 30-m-long fiber is considered to be the best choice     

Picosecond structure in self-pulsing GaAs injection lasers

Partial mode locking has been observed in self-pulsing GaAs injection lasers using an optical correlation technique. The lasers are operated at room temperature and the self-pulsing occurs near the end of the injection current pulse. The pulsewidths are about 4 ps, which are the shortest observed in an injection laser.     

Signal structure of continuously self-pulsing GaAs lasers

CW-excited GaAs lasers can emit self-induced pulses. To study these pulses we have used an intensity correlator involving phase-matched second-harmonic generation in LiIO3. Besides measuring the pulsewidth and the repetition rate we investigated the amplitude fluctuations within a pulse and the correlation between fluctuations of consecutive pulses.     

A simple model describing both self-mode locking and sustained self-pulsing in ytterbium-doped ring fiber lasers

This paper presents a model describing self-mode locking (SML) and sustained self-pulsing (SSP) in a unidirectional ring-fiber laser using only the interaction between the saturated population inversion and the optical signal circulating in the laser cavity. Gain saturation alone is used to explain SML behavior close to laser threshold and the sharp transition to an SSP regime. The model also describes self-pulsing inhibition to the profit of SML for a sufficiently high pump power. Experimental results agree with most model predictions, but the overestimation of the self-pulsing threshold suggests that the phenomenon is furthered by an effect other than gain saturation.     

Efficient and tunable Er/Yb fiber grating lasers

Efficient and tunable single-frequency fiber Bragg grating (FBG) lasers are demonstrated using a novel photosensitive Er/Yb fiber design. Both sub-mW threshold pump power, and high slope efficiencies of ~31% at 1536 nm and ~26.1% at 1562 nm were achieved. Wavelength tuning could be obtained over 11 and 25 nm in 1535 and 1550 nm wavelength regions, respectively, by cavity-length tuning     

Stability of self-pulsing due to Hopf bifurcation in semiconductor lasers

A formulation is given of the stability criterion for oscillations arising at Hopf bifurcations in semiconductor lasers. A second-order perturbation expansion is utilized to provide nonlinear rate equations for the laser. The rate equations contain terms whose second-order partial derivatives are required in the definition of stability parameters. Using these parameters, a simple statement of the stability criterion is possible. Numerical calculations are included, using typical device parameters, and show the existence of both stable and unstable Hopf oscillations.     

Perturbation solution of self-pulsing in semiconductor lasers witha saturable absorber

We solve the three-component rate equations for semiconductor lasers with a saturable absorber or for multi-section semiconductor lasers by using a singular perturbation method. The effects of nonlinear gain and spontaneous emission are included in the rate equations. By transforming the rate equations to the generalized coordinates, we eliminate the most rapidly varying term adiabatically for the fast saturable absorber. Then, we solve the two-component nonlinear equations to obtain analytic expressions for parametric dependence of self-pulsing amplitude and self-pulsing frequency. the self-pulsing frequency shifts from the small-signal oscillation frequency to the lower-frequency side as we increase the self-pulsing amplitude. The square of the self-pulsing frequency does not linearly depend on the injection current, in agreement with experimental observations. We also derive an optimum saturable absorber recovery time for the shortest optical pulse generation     

光纤参数对双包层Er3+/Yb3+共掺光纤激光器的影响

为了研究掺杂浓度、包层尺寸对双包层Er3+/Yb3+共掺光纤激光器的影响,根据双包层Er3+/Yb3+共掺光纤激光器产生激光的机理,基于速率方程,采用改变Er3+,Yb3+掺杂浓度、内包层尺寸等光纤参数的方法,得到了双包层Er3+/Yb3+共掺光纤激光器随光纤参数变化的特征结果。结果表明,在Er3+掺杂浓度不变的情况下,增大Yb3+的掺杂浓度,可有效地提高激光器的输出功率;在Yb3+掺杂浓度保持不变的情况下,增大Er3+掺杂浓度,也可提高激光器的输出功率,但提高的幅度不明显;减小内包层尺寸,激光器的最佳光纤长度随之减小。     

LD泵浦掺镱的双包层光纤激光器的研究

本文通过数值分析对线形腔LD泵浦掺镱的双包层光纤激光器进行研究,分析了不同泵浦方式下的泵浦光、激光输出功率和增益特性在光纤中的分布。结果表明,双端非对称泵浦比较适合高功率光纤激光器。进一步又研究双端非对称泵浦输出功率与光纤长度及腔镜反射率的影响,为提高光纤激光器的输出功率提供了理论和实验依据。     

一种可调谐掺铒光纤激光器的研究

文章基于掺铒光纤在1 550 nm波段的增益特性,利用光纤光栅作为调谐装置,设计了可调谐光纤光栅激光器的简单结构,通过改变光纤光栅的温度对光纤激光嚣的波长进行了调谐.更重要的是实验分析了不同掺铒光纤长度对激光输出功率的影响,在温度为25℃时,实验中分别取10、20和30 m 3种不同光纤长度进行了测试,结果表明,不同长度的掺铒光纤,其阀值不同.     

基于啁啾脉冲放大的掺铒全光纤结构激光器

为了使全光纤结构啁啾脉冲放大实现超短激光的脉冲输出,采用色散补偿光纤对种子脉冲进行了展宽,利用普通单模光纤来实现放大后脉冲的压缩。对整体激光系统进行了理论分析和实验验证,获得了420fs的超短激光脉冲,平均功率达到1.81W。并利用周期极化的铌酸锂晶体对放大激光脉冲进行倍频,将激光波长拓展到近红外的780nm附近,光谱半峰全宽达到11nm。结果表明,在全光纤结构的掺铒光纤激光系统中,可以通过改变色散光纤的插入量对脉冲展宽和压缩过程中光谱畸变进行有效的控制。这一结果对于实现高功率的全光纤超短脉冲放大系统是有帮助的。     

Frequency instability in Er/Yb fiber grating lasers due to heatingby nonradiative transitions

Heating of the Er/Yb-codoped fiber lasers due to strong pump absorption was found to cause large frequency fluctuation in addition to lasing wavelength shift. Laser frequency fluctuation of up to 1.7 GHz was measured by using an absorption line of an acetylene gas cell. The large frequency fluctuation was reduced to less than 80 MHz with proper cooling of the laser     

损耗对掺镱双包层光纤激光器输出特性的影响

本文分析了损耗对线形腔掺镱双包层光纤激光器输出特性的影响。对有损耗的线形腔掺镱双包层光纤激光器输出特性进行了数值分析,(当考虑光纤损耗时)得出了泵浦功率和正反向激光功率在2 0米长光纤处有近2W降低(泵浦功率为2 0W时)的结论。同时,文中给出了有损耗时的输出功率与光纤长度、泵浦功率和后镜反射率R2 的关系曲线。