Output Characteristics of High-Power Continuous Wave Raman Fiber Laser at 1484 nm Using Phosphosilicate Fiber

A continuous wave (CW) high-power Raman fiber laser (RFL) with maximum output power of 2.24 W and slope efficiency of 32.8% at 1484 nm is obtained using a CW 8.4 W/ 1064 nm Yb-doped double-clad fiber laser as a pump, 700 m phosphosilicate fiber, and cascaded cavities with two pairs of fiber Bragg grating mirrors for the first and the second Stokes orders. Theoretical simulation of the RFL using a very efficient and rapidly converging collocation method is done to understand and optimize the fiber length to obtain maximum second Stokes power. RFL performance for the 300, 700 and 1150 m phosphosilicate fiber lengths was experimentally investigated by observing maximum output power, slope efficiency, threshold power, and full-width at half maximum at the second Stokes wavelength.     

Simultaneous Double-Color Continuous Wave Raman Fiber Laser at 1239 nm and 1484 nm Using Phosphosilicate Fiber

Simultaneous double-color high-power continuous wave (CW) Raman fiber laser at 1239 nm and 1484 nm is demonstrated which uses CW 8.4 W Yb-doped double-clad fiber laser at 1064 nm as a pump, 1 km phosphosilicate fiber, and cascaded cavities consisting of two pairs of fiber Bragg grating (FBG) mirrors. Maximum output powers are 0.65 W at 1239 nm and 0.97 W at 1484 nm with a 50%/50% output mirror reflectivity pair, and 0.37 W at 1239 nm and 1.06 W at 1484 nm with a 75.5%/50% pair. The output characteristics of this laser for different FBG mirror reflectivities are reported.     

内腔级联拉曼光纤激光器输出特性的实验研究

采用标准单模石英光纤作为拉曼增益介质，光纤布拉格光栅作为谐振腔镜，研制了一台内腔级联拉曼光纤激光器。利用掺Yb双包层光纤激光器作为抽运源，实现了二级拉曼转换，在波长1176.8nm获得了309mW的最大输出功率，斜率效率接近51.5％。在小抽运功率下，发现拉曼光纤激光器的输出中存在重复周期约为2.9μs的脉冲序列；当抽运功率大于某一值时，上述脉冲消失，获得了十分稳定的连续输出。     

800 mW/1484 nm highly efficient two-cascaded phosphosilicate Raman fiber laser pumped by Nd:YVO4 solid-state laser

Using 1064 nm CW Nd:YVO₄ solid-state laser as a pump, 1-km phosphosilicate fiber and cascaded cavities with two pairs of fiber Bragg grating mirrors for 1239 and 1484 nm, we obtained a CW 800 mW/1484 nm Raman fiber laser (RFL) for an actual incident pump power of about 2 W (Nd:YVO₄ power of 6.90 W). The conversion efficiency is as high as 40%. To the best of our knowledge, this is the highest conversion efficiency of RFL pumped by solid-state laser. The output power instability at 1484 nm in half an hour is less than 3%. In addition, the numerical simulations are also performed. Good agreement between the results of numerical simulation and the results of the experiment has been demonstrated.     

输出功率稳定的二级喇曼光纤激光器特性

提出一种输出功率稳定的二级喇曼光纤激光器,从理论分析角度探讨了它的特性.结果表明：由于在抽运光的二级斯托克斯光频附近的自发辐射光的钳制作用,激光器的一级和二级输出功率几乎都不受抽运功率波动的影响,从而降低了抽运光低频相对强度噪音转移|激光器输出的一级和二级斯托克斯光功率都很稳定,并且通过调节激光器结构中的可变衰减器,可以有效控制一级、二级激光的输出功率以及它们的比值.这些特性表明该喇曼光纤激光器很适合于作为喇曼光纤放大器的抽运源.     

Suppression of pump-to-Stokes relative intensity noise transfer in Raman fiber laser by injection of modulated signal

A feasible approach is theoretically demonstrated that suppresses the relative intensity noise (RIN) transfer from pump sources to the proposed Raman fiber laser (RFL) output at the first-order Stokes line. The technique is accomplished by injecting a modulated signal at second-order Stokes shift from the pump wavelength according to the monitored RFL output, which indirectly consumes the pump power fluctuations and results in suppression of the RIN transfer to the RFL output. With the RFL used as a pump source for co-pumped Raman fiber amplifiers, further calculation results show that the Q-factor penalty due to RIN transfer can be dramatically reduced.     

Dual-order Raman fiber laser with suppressed low-frequency pump-to-stokes RIN transfer

By employing an output-power clamping technique, a dual-order Raman fiber laser (RFL) is theoretically presented with suppressed low-frequency relative-intensity-noise (RIN) transfer from pump sources to both first- and second-order Stokes output. Their powers can be easily tuned in a large dynamic range. Furthermore, the second-order output power can be individually controlled, which makes it flexible to adjust the ratio of the first- to second-order output power. In addition, the stabilization of low-power second-order output is also accomplished in the RFL setup. These properties fit the proposed RFL for use as dual-order pump sources in Raman fiber amplifiers.     

用于光纤拉曼放大器抽运源的单级光纤拉曼激光器

抽运光源是光纤拉曼放大器应用于密集波分复用系统的关键技术,设计了一种紧凑型的808nm激光二极管抽运的基于钒酸钇（Nd^3＋：YVO4）晶体1342nm固体激光器模块,提出利用上述1342nm固体激光器抽运基于光纤光栅的单级全光纤型拉曼谐振器获得1．4μm激光输出的光纤拉曼激光器,分析了固体激光器的阈值特性、性能优化方法和单级光纤拉曼谐振器的设计方法。上述1342nm固体激光器模块在抽运功率2W时获得了最大655mW的激光输出功率和42．6％的斜率效率,单级拉曼谐振器的1342nm到1．4μm光功率转换斜率效率达75％,在1425nm、1438nm、1455nm和1490nm处的输出功率达到300mW以上。最后给出基于1．4μm光纤拉曼激光器抽运的宽带平坦放大的光纤拉曼放大器的结构参量和性能测试结果。     

Highly efficient cascaded P-doped Raman fiber laser pumped by Nd:YVO4 solid-state laser

A highly efficient cascaded P-doped Raman fiber laser （RFL） pumped by a 1064-nm continuous wave （CW） Nd：YVO4 solid-state laser is reported. 1.15-W CW output power at 1484 nm is obtained while the input pump power is 4 W, corresponding to the power conversion efficiency of 28.8%. The threshold pump power for the second-order Stokes radiation is 1.13 W. The slope efficiency is as high as 42.6%. The experimental results are in good agreement with theoretical ones. Furthermore, the power instability of the P-doped RFL at 1484 nm in an hour is observed to be less than 5%.     

Characterization of an Intra-Cavity Pumped P2O5-Doped Silica Raman Fiber Laser

We examine the characteristics of a P₂O₅-doped Raman fiber laser pumped by a double-clad ytterbium-doped fiber laser in an intra-cavity configuration. The double-clad fiber laser consists of two high reflection fiber Bragg gratings at 1092 nm, with an active length of 17 m, where the output grating is located at the end of the 400m P₂O₅-doped fiber. The Raman cavity is formed by a 1278-nm-high reflection fiber Bragg grating spliced to the double-clad fiber, and a 50% output coupler. The maximum conversion efficiency at 1278 nm with respect to the input pump power at 915 nm was 26.9%.     

采用国产大模场面积双包层光纤的714W连续光纤激光器

采用两个中心波长约976 nm准直输出的高功率半导体激光模块为抽运源,通过空间滤波和非球面透镜耦合技术,双端抽运长度为21 m的大模场面积国产掺镱双包层光纤,获得了714.5 W的高功率连续激光输出。采用反向抽运,当入纤抽运功率为760 W时,激光输出功率达到501 W;采用双端抽运,当入纤抽运功率为1137 W时,获得了714.5 W的高功率连续输出,光光转换效率为62.8%,斜率效率为67%。     

基于光纤环形激光器和光放大的100 km光纤布拉格光栅传感系统

在基于掺铒光纤-拉曼混合放大的可调光纤环形激光器的光纤布拉格光栅(FBG)传感系统结构基础上,提出了延长传感距离的新方法。该方法以环形掺铒光纤激光器作为光源,采用双波长拉曼放大的方法对信号进行低噪声的双向放大,系统中间的两段掺铒光纤再利用剩余的抽运功率产生自发辐射光和放大传感信号,使得整个系统能够在超长的传感距离上获得很高的信噪比。实验表明使用一只40 mW的掺铒光纤放大(EDFA)抽运源、一只170 mW的拉曼抽运源和一只2 W的拉曼抽运源,可以使整个系统的传感距离达到100km,并且传感系统的光纤布拉格光栅反射信号均能获得超过57 dB的优良信噪比,从而实现在超长距离上的光纤布拉格光栅传感。     

1410 nm波段分布式光纤拉曼增益放大器的研究

讨论了分布式光纤拉曼增益放大器的工作原理,采用1320nm固体激光器作为抽运源,获得了1410nm波段附近的光放大,在单模GI光纤长度为23km时,初步研究了拉曼放大器增益与光纤作用长度的关系,抽运脉冲峰值功率分别为50W、30W时,光纤的有效作用长度分别为15．5km和10.5km;研究了在不同的光纤有效作用长度时,拉曼放大器增益与抽运功率的关系;从光纤拉曼光谱图估算了光纤拉曼放大器的光谱宽度为50nm或250cm^-1。     

Theoretical analysis and heat dissipation of mid-infrared chalcogenide fiber Raman laser

Based on the structure of mid-infrared chalcogenide fiber Raman laser, the nonlinear coupled equations and heat dissipation equations are constructed. The effects of laser parameters including pump power, fiber length, reflectance of output coupler and fiber loss coefficient on laser performance are numerically analyzed. The results show that the Raman laser pumped at 2 μm can operate at high slope efficiency using the optimized structure parameters. In addition, the output laser power decreases dramatically with the increasing of fiber loss coefficient. Moreover, the temperature distributions along the fiber radial and axial directions and the maximum temperature versus launched pump power are calculated according to the heat dissipation equations. The results show that the maximum temperature in the fiber increases dramatically with the increasing launched pump power, which is above 300 °C for launched pump power of 21 W. The above obtained results can be used for theoretical guiding and optimizing design of practical chalcogenide fiber Raman laser.     

大功率多波长可转换双包层光纤激光器

在多模掺镱双包层光纤上,利用相位掩模法直接写制Bragg光栅作为激光器后腔镜,得到多波长激光输出.在室温下,通过调节偏振控制器可以得到稳定的单波长及多波长的激光输出,输出波长范围在1 056～1 061 nm,线宽均小于0.02 nm.在25 W的976 nm激光泵浦下,激光器得到功率为6 W的多波长输出.     

高能掺镱离子光纤激光器的研究

从激光器的速率方程出发,对光纤激光器的工作原理以及输出特性进行了研究,得到了光纤激光器在稳态条件下阈值条件和激光器输出功率的表达式.利用数值模拟结果对光纤激光器基本参量进行分析和论证.为光纤激光器的优化设计提供理论依据.并提出了全光纤型光纤激光器的实验方法.获得了最大功率7.5 W、波长1080 nm、峰值半宽0.11 nm的连续单模激光输出.     

高功率宽调谐范围掺Yb3+光子晶体光纤激光器

采用闪耀光栅作为色散元件,构建了前向、后向输出两种结构的可调谐掺Yb3 光子晶体光纤激光器,并对其输出特性进行了分析研究.在抽运功率5.75W时,前向输出结构实现了1050.6～1110.2 nm的连续调谐输出,光谱线宽约0.1 nm,边模抑制比大于44 dB.在调谐激光波长为1085 nm时,得到最高输出功率677 mW.结构改进的后向输出结构的可调谐输出结构在抽运功率4.43 W,调谐波长1075 nm,实现了2.21 W的功率输出,斜率效率为73%;调谐范围50.9 nm(1042.1～1093 nm),光谱线宽小于0.08 nm,边模抑制比大于50 dB.两种结构的可调谐激光器输出均为线偏振光,偏振度大于89.5%.     

用光纤回路镜组成运转在1240 nm的新型串级光纤拉曼激光器

由光纤回路镜组成的新型串级光纤拉曼激光器,用1064nm作为抽运源,光纤拉曼激光运转于第三级斯托克斯串级拉曼波段,输出波长为1240nm。在光纤回路镜的性能和光纤参数还不够完善的条件下,1240nm输出功率为300mW,光－光转换效率约为25％。     

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.     

976 nm激光抽运二氧化硅微球级联拉曼散射激光的研究

利用电极放电产生的电弧高温熔融二氧化硅单锥细纤, 熔融的二氧化硅在表面张力作用下形成表面光滑的微球, 完成高品质因子微球腔的制备. 将976 nm激光通过锥光纤以倏逝场方式高效耦合入微球, 研究具有高能量密度回廊模的微球腔中的三阶非线性现象——受激拉曼散射现象. 在实验中测得了六级级联的拉曼散射激光, 各级拉曼散射激光分别测得单纵模或多纵模; 在抽运光功率不少于582.6 μW时, 测得位于1200 nm附近的拉曼散射激光; 当抽运光功率为3.014 mW时, 测得位于1287.04 nm附近的第六级拉曼散射激光. 关键词： 微球腔 锥光纤 高品质因子 拉曼散射激光