掺镱双包层光纤激光器典型参数对斜线效率的影响

分析了双包层光纤激光器(DCFL)耦合方程的解析解，并对信号光散射损耗、后腔镜泵浦反射率等影响掺镱DCFL斜线效率的典型参数进行了理论研究。结果表明，斜线效率并不是随着后腔镜泵浦反射率的升高而单调增大，因为泵浦反射率的升高会影响光纤的最佳长度，从而降低斜线效率。所以在优化斜线效率时应该考虑到泵浦反射率和光纤最佳长度之间的匹配。同时，提高纤芯掺杂浓度、减小信号光散射损耗也能增大斜线效率。     

LD泵浦的准连续输出双包层掺镱光纤激光器

介绍了光纤激光器的理论模型和结构组成,搭建了976nm激光二极管（LD）泵浦的准连续输出双包层掺镱光纤激光器系统。制作了激光脉冲电源方波发生电路,该电源在脉冲工作模式下重频≤1000Hz,脉宽从10μs-50ms可调,占空比≤50％。分析了稀土掺杂双包层光纤的各项性能和能级系统,并实验研究了准连续掺镱双包层光纤激光器的输出特性。在最大泵浦功率为8．12w,重频为50Hz和脉宽为10ms下,测得其最大脉冲输出功率为2．67w。     

利用光纤光栅的高功率掺镱光纤激光器

报道了利用一对光纤光栅作为双包层Yb^3 掺杂光纤激光器的谐振腔，激光二极管光纤模块(LD)进行了抽运，并采用锥形光纤实现了全光纤化结构，获得了高功率双包层光纤激光器。光纤光栅通常是用融接技术实现与双包层光纤的一体化连接的，采用的双包层光纤为内包层为梅花瓣形结构的掺Yb^3 离子的石英光纤，采用的抽运源为中心波长为970nm的半导体激光光纤输出模块，在抽运源电流达到2．4A时，获得了10．8W的光纤激光器单横模输出，输出波长1100．5nm，峰值半峰全宽(FWHM)为0．54nm，激光器斜效率为59％。     

高效率可调谐掺镱双包层光纤激光器研究

研究了一种高效率可调谐掺镱双包层光纤激光器,在抽运半导体激光为915nm、功率为1W的条件下,掺镱双包层光纤激光器的最大输出功率为440mW,输出斜效率约为80％。输出光束的M^2因子为：x方向1．06,y方向1．04。用一光栅作为输出耦合,输出波长可在1070nm-1150nm的范围内调谐。     

脉冲泵浦掺镱双包层光纤激光器的动力学研究

对脉冲泵浦的掺镱双包层光纤激光器进行了实验研究.采用重复频率1-10 kHz、脉宽100 μs的976 nmLDs泵浦,实现了脉宽小于10 ns的稳定激光脉冲输出.并对该激光器的动力学过程进行了分析,首次提出了在脉冲泵浦光纤激光器中产生ns脉冲是瑞利散射和受激布里渊散射共同作用的结果.     

国产掺镱双包层光纤的激光特性

采用MCVD方法研发了掺镱双包层光纤,并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400/450μm,数值孔径为0.36,纤芯直径约为16μm,数值孔径约为0.18。荧光谱线的范围为1 000~1 140 nm,1 030 nm处的峰宽大于50 nm。采用大功率激光二极管单端泵浦6 m长的双包层光纤,在泵浦入纤功率为61 W时, 获得了32 W的激光输出,斜率效率为64%。该光纤在高功率处未发现饱和现象,通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率激光器件。     

国产掺镱双包层光纤的激光特性

 采用MCVD方法研发了掺镱双包层光纤,并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400/450μm,数值孔径为0.36,纤芯直径约为16μm,数值孔径约为0.18。荧光谱线的范围为1 000~1 140 nm,1 030 nm处的峰宽大于50 nm。采用大功率激光二极管单端泵浦6 m长的双包层光纤,在泵浦入纤功率为61 W时, 获得了32 W的激光输出,斜率效率为64%。该光纤在高功率处未发现饱和现象,通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率激光器件。     

后腔镜对掺镱双包层光纤激光器输出特性影响研究

使用国产掺镱双包层光纤搭建了双包层激光器实验系统.将透射率不同的反射镜作为后腔镜进行了激光器输出激光光谱和功率测量.根据激光器数学模型和增益理论,分析了实验中后腔镜参量对激光器输出特性的影响,并深入讨论了后腔镜透射率与激光器输出波长之间的关系.实验表明：后腔镜与激光器输出激光功率和波长紧密联系,通过调节后腔镜的透射率可以优化系统的输出激光特性.     

LD泵浦掺镱双包层光纤激光器的理论研究

对线形腔LD泵浦掺镱的双包层光纤激光器进行研究,通过数值模拟,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,单端后向泵浦输出功率率较高,对于小功率光纤激光器则是最佳选择。进一步又研究了单端后向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。     

掺镱双包层光纤激光器的径向偏振振荡

通过在腔内放置汇聚型布儒斯特角轴锥体,并对增益光纤采用双端泵浦, 实验上实现了掺镱双包层光纤激光器的径向偏振模振荡.对增益光纤的末端做了斜角抛光,抑制了光纤端面间的寄生振荡,减小了在低泵浦功率下被放大的自发辐射光份额.该激光器的域值约为175 mW,斜率效率13.8%,激发波长约1085 nm.当泵浦功率达到最大值460 mW时,获得了39 mW的激光输出功率,其光束偏振纯度和圆柱形对称性有显著改善.     

Core temperature in super-Gaussian pumped air-clad photonic crystal fiber lasers compared with double-clad fiber lasers

In this paper we investigate the core temperature of air-clad photonic crystal fiber (PCF) lasers pumped by a super-Gaussian (SG) source of order four. The results are compared with conventional double-clad fiber (DCF) lasers pumped by the same super-Gaussian and by top-hat pump profiles.      

An approximate analytic solution of strongly pumped Yb-doped double-clad fiber lasers without neglecting the scattering loss

A theoretical analysis of strongly pumped Yb-doped double-clad fiber lasers is presented and an approximate analytic function of distributed laser along the whole fiber with the scattering loss is obtained for the first time. A comparison is made between the analytic solution and the exact numerical solution. The results have shown that the analytic function of distributed laser within the fiber is accurate and explicit. With the analytic solution the losses caused by laser scattering are shown in three different pump modes. The results verify that the backward pumping can get the highest output power in strongly pumped fiber lasers.     

Theoretical and experimental investigation of thermal effects in a high power Yb-doped double-clad fiber laser

In this paper, based on the thermal conduction equations and the steady-state rate equations, a theoretical and numerical analysis of thermal effects is investigated for a single end pumped Yb-doped double-clad fiber laser (YDDC). The distributions of signal power and temperature for different pump powers and fiber parameters are compared. According to the results, the parameters of the optical-cavity have been optimized and an effective method has been adopted to reduce the thermal effects in an experimental investigation. As a result, an output power of 621 W has been obtained with a slope efficiency of 78%.     

2 W Yb-doped double-clad fiber superfluorescent source with 42 nm 3 dB bandwidth

The output spectrum of Yb-doped double-clad fiber superfluorescent source (SFS) is tailored by placing a broadband dichroic mirror in the pump end of conventional single-pass forward configuration, which constitutes double-pass forward configuration. The 3 dB bandwidth is increased from 11 to 42 nm. A maximum output SFS power of 2.12 W and a slope efficiency of 43.2% are obtained. The double-clad fiber is 25 m and the pump power is adequate to saturate the fiber as far as the feedback-induced lasing appears.     

A theoretical and experimental study on all-normal-dispersion Yb-doped mode-locked fiber lasers

We report on a theoretical and experimental study of an all-normal-dispersion (ANDi) Yb-doped mode-locked fiber laser, in which nonlinear polarization rotation (NPR) is used to realize mode-locking without any dispersion compensation. Based on the coupled nonlinear Schrdinger (CNLS) equation, a model simulating the mode-locked process of an allnormal-dispersion ring fiber laser is developed, which shows that the achievement of stable mode-locking depends on the alignment of the polarization controller (PC) along the fast-polarization axis of the fiber, the birefringence intensity, and the net cavity dispersion. According to the theoretical analysis, stable mode-locked pulses with pulse duration 300 ps and average output power 33.9mW at repetition rate 36MHz are obtained.     

Numerical analysis of stimulated Brillouin scattering in high-power double-clad fiber lasers

A theoretical analysis of stimulated Brillouin scattering (SBS) in linear cavity Yb³⁺-doped double-clad fiber lasers is presented by solving the steady-state rate equations with the SBS. The effects of cavity length, fiber core diameter, input mirror reflectivity at Stokes wavelength, Yb³⁺ concentration and laser linewidth on the SBS are discussed. Numerical results show that the SBS threshold power can be improved by shortening the cavity length, using large mode area fiber, reducing the input mirror reflectivity at Stokes wavelength, lowering the Yb³⁺ concentration and broadening the laser linewidth, and the influence of the laser linewidth on the SBS threshold power is more noticeable than other system parameters.     

Numerical analysis and experimental results of output performance for Nd-doped double-clad fiber lasers

Numerical analysis is investigated for the high-power double-clad fiber lasers and experimental results using different microscope objectives for focusing into a Nd-doped rectangular double-clad fiber also performed. The numerical analysis includes dependence of output power on output mirror reflectivity, absorbed pump power, loss, and fiber length and pump power distribution for the cases of one-end and two-end pumps with 20 dB/km loss. Calculated conversion efficiencies are 76.36%, 69.73%, and 63.84% for lossless, two-end pump, and one-end pump fiber lasers, respectively. Slope efficiencies from absorbed pump power/output powers measured using microscope objectives are 16.8%/182 mW, 53.8%/351 mW, 24.9%/1240 mW, and 13.9%/649 mW for magnifications of 5×, 10×, 20×, and 40×, respectively.     

The analytical investigation of the super-Gaussian pump source on the thermal, stress and thermo-optics properties of double-clad Yb:glass fiber lasers

Fiber lasers have attracted considerable attention when their power can realistically be scaled to kilowatt level and beyond. In this paper, we assumed that the fiber core and first clad are exposed to a pump source with a super-Gaussian profile of order four. The effects of this non-uniform heat deposition on thermal, stress and thermooptics properties such as temperature-dependent change of refractive index and thermally induced stress have been comprehensively studied and their equations analytically derived.     

Influence of stimulated Brillouin scattering on the temporal dynamics of an actively Q-switched double-clad fiber laser

The role of stimulated Brillouin scattering (SBS) during the active Q-switching of a typical high power double-clad fiber laser is experimentally and theoretically investigated. Our numerical model reproduces multiples Brillouin Stokes generation and the fast temporal dynamics which were experimentally observed. It clearly demonstrates that SBS is the cause of peak power enhancement effects such as giant pulse generation. The pulse formation process during the active Q-switching and the precise role of SBS in the pulse narrowing is detailed.     

Dual-wavelength high-power Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating

We report a high-power dual-wavelength Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating (FMFBG). The FMFBG was fabricated by using a piece of fiber in a length of fiber with a cutoff wavelength of 1225 nm, which supported two modes at 1060 nm. The laser was pumped by a fiber pigtailed laser diode working at 915 nm. Single-wavelength, dual-wavelength and triple-wavelength laser oscillations were observed when the fiber laser operated under different low pump powers. However, stable dual-wavelength operation was achieved at higher pump power of 3.9 W and remained unchanged until the output power reached 5.67 W under the maximum available pump power of 10.7 W. The laser wavelengths were centered at 1059.12 and 1060.80 nm with a full-width at half-maximum of 37 and 43 pm, respectively. The signal-to-noise-ratio was greater than 50 dB and the beam quality factor (M²) was about 1.9.