脉冲泵浦的掺镱光纤放大器中放大自发辐射动态变化模拟

在低重复率、高能量脉冲的应用场合,光纤放大器中采用脉冲泵浦的方式具有重要意义.本文模拟了脉冲泵浦方式下掺镱双包层增益光纤中放大自发辐射功率的动态变化,为优化脉冲泵浦方式提供了参考.通过有限元分析方法求解光纤中镱离子的速率方程和各光场的功率传输方程,模拟了正向泵浦条件下,泵浦脉冲开始后0~740 μs时间内光纤内部正向、反向放大自发辐射功率分布情况的动态变化以及光纤两端放大自发辐射输出功率随泵浦时间的变化.模拟结果发现了光纤两端正向、反向放大自发辐射功率增长速度的差异之处,以及光纤内部两种放大自发辐射功率分布动态演变的一些特征.     

高功率光纤激光器中ASE噪声的测量方法（英）

高峰值功率脉冲光纤激光器在激光雷达系统中有着广泛的应用。然而,光纤激光器中放大自发辐射噪声（ASE）严重影响了系统的探测性能。提出一种测量高峰值功率脉冲光纤激光器中ASE噪声的方法。在该方法中,首先对高峰值功率的激光脉冲衰减,然后在时域分别测量和计算ASE噪声和激光脉冲的相对能量。给出了光纤激光器在驱动电流分别为6 A,7 A和8 A时衰减后的ASE噪声廓线以及ASE噪声占激光脉冲能量的比例。     

Amplified spontaneous emission properties of a single mode Er3+-doped tellurite fiber

Spectral characteristics of the amplified spontaneous emission(ASE)from a novel single mode Er3+ doped tellurite fiber with D-type cladding is reported in this letter.When pumped at 980 nm,an ASE source that has nearly a 100-nm flat FWHM bandwidth is obtained with a fiber length of 30-60 cm. Variation of ASE spectra with pump powers and fiber lengths are measured.Output power up to 2.0 mW is obtained with a launched pump power of 660 mW.     

旋光纤喇曼放大器中ASE噪音模型及仿真计算

通过分析旋光纤喇曼放大器中信号光、抽运光的非线性薛定谔波动方程及放大自发辐射噪音特性,提出一种能同时在旋光纤喇曼放大器中产生预计波形放大自发辐射噪音,又方便计算的方法.根据放大自发辐射噪音时域特性,建立并在波动方程中加入放大自发辐射非高斯噪音模型.在考虑旋光纤双折射的非线性效应同时,通过分步傅里叶法对波动方程求解,计算了旋光纤喇曼放大器中的放大自发辐射噪音,并与实验结果吻合.     

一种结构新颖的L波段掺铒光纤激光器

提出了一种结构新颖的L波段环形腔掺铒光纤激光器。用掺铒光纤作为增益介,采用980nm激光器作为前向抽运源,利用起偏器和偏振控制器获得L波段激光,利用光环形器将后向的放大自发辐射再引入铒光纤的前端,重复利用。当抽运功率为103mW时得到了阈值功率约为23．87mW,输出功率达6．34mW的激光输出,斜率效率约为8．05％,与没有重复利用后向放大自发辐射谱的掺铒光纤激光器做比较,该结构对L波段掺铒光纤激光器的性能有明显的提升作用。对于长度不合适的铒纤,在没有重复利用后向放大自发辐射谱时没有获得激光输出;而在利用后向放大自发辐射后,在阈值功率约为88mW时得到了激光输出,从而很好地证明了上述结论。     

光纤放大器放大自发辐射特性与高温易损点位置

在高功率光纤放大器实验中,时常发现增益光纤抽运注入熔接点后10—50 cm处容易发生光纤烧毁现象.为了对该现象进行理论预测,基于光纤激光器速率方程模型和增益光纤的热传导模型,从种子功率、抽运功率和抽运吸收三个方面对掺镱双包层光纤放大器中的放大自发辐射(ASE)和温度特性进行研究.结果表明,在放大倍率较高、ASE较为严重等情况下,光纤放大器中的最高温度点一般不在抽运注入的熔接点处,而在距离熔接点10—50 cm处,与实验中发现光纤烧毁的位置基本符合.从光纤放大器的ASE抑制、最高温度点温度控制角度出发,对光纤放大器在种子功率、抽运功率、抽运吸收、放大倍率和抽运波长等方面的设计给出了指导性的建议.     

Influences of ASE on the performances of Q-switched ytterbium-doped fiber lasers

The output characteristics of actively Q-switched ytterbium-doped fiber lasers (YDFL) are investigated in this paper. Our experimental results show that, the combined effect between the short switching time and the gain transient property of doped fiber causes the initial amplified spontaneous emission (ASE) power fluctuation, forming the multi-peak structure in the output pulse for either ring or linear cavity Q-switched YDFL. The pulse buildup time decreases with the rising of the pump. Moreover, since the broad-band ASE generated in the YDF is very high, it may saturate the doped fiber once the switch has been opened, making it difficult to achieve Q-switched laser oscillation for both fiber lasers. By using ASE filter to suppress the initial ASE, the gain supplied by the YDF can be greatly enhanced, which can not only decrease the threshold, but also greatly decrease the duration, and enhance the peak power of the Q-switched laser pulse as well. By using such an ASE filter, the Q-switched laser pulse with the peak power of 40.7 W and the duration of 30 ns has been achieved for the linear cavity YDFL pumped with 160 mW.     

一种高效率的L波段掺铒光纤ASE宽带光源

利用双程双向泵浦单级掺铒光纤的结构实现高效率的L波段掺铒光纤放大自发辐射输出,同时选择1480nm半导体激光器作为泵浦源,高掺杂铒光纤为增益介质,通过优化铒光纤长度,获得了在1566-1604 nm（38 nm）,自发辐射谱功率高于－16 dBm,总输出功率13.7 dBm的L波段掺铒光纤放大自发辐射光源.该光源结构相比于双程前向泵浦结构的L波段掺铒光纤放大自发辐射光源,其泵浦效率从11.8%提高到23.4%.     

Output power improvement in an Yb-doped fiber laser with an additional unpumped Yb-doped fiber

Master oscillator power amplifier (MOPA) technology has been widely used in high-power or ultrashort-pulse fiber laser systems because the shape of the laser pulse can be easily adjusted. Usually, the first amplification stage of a 1064 nm fiber laser uses the core-pumped Yb-doped fiber amplifier (YDFA); however, the gain or output power is limited owing to the strong amplifier spontaneous emission (ASE) in the 1030 nm band. This paper presents the improved output power in an YDFA by inserting an additional unpumped Yb-doped fiber, which absorbs the lost backward ASE emitted from the pump end. We achieved an output power increase of more than 10% in a low-power signal, and the increase in output power decreased as the signal power increased. Moreover, the insertion of an additional unpumped Yb-doped fiber restricted the unwanted 1030 nm lasing in a low-power signal.     

Simulation analysis of one-stage C+L-band erbium-doped fiber ASE source with double-pass bi-directional pumping configuration

A new technique to generate a C+L-band flat amplified spontaneous emission (ASE) source in one-stage erbium-doped fiber (EDF) using bi-directional pumping configuration is analyzed. The simulation results show that the key point of obtaining flat C+L-band ASE spectrum in one-stage EDF is using a laser diode operated at 980 nm as backward pump source. ASE source with nearly 80-nm bandwidth can be obtained by means of selecting suitable fiber length and properly adjusting the ratio of forward to backward pump power.     

掺镱光纤放大器泵浦脉宽优化

为抑制低重复频率高能脉冲光纤主振荡功率放大(MOPA)系统的放大自发辐射(ASE)效应,达到脉冲泵浦的最佳放大效果,需要对泵浦脉宽进行优化。基于求解速率方程和功率传输方程,理论研究了脉冲泵浦下掺镱光纤放大器上能级粒子数密度、光纤内存储能量、正反向放大自发辐射的瞬态响应。在给定的泵浦功率、光纤长度、纤芯面积和掺杂数密度等参数下,数值计算得到的优化泵浦脉宽为793 s。此外,实验测定了ASE的建立时间; 通过调节泵浦脉宽,测定了脉冲泵浦下掺镱光纤放大器的放大效果,实验中得到的泵浦脉宽的优化值为800 s,证明了数值模拟的正确性。     

新颖的双通道输出高功率掺铒光纤宽带光源

在分析L波段放大自发辐射(ASE)谱产生原理的基础上,设计出一种新颖的双级结构掺铒光纤ASE宽带光源,该光源可在两个端口分别输出高功率的C波段和L波段的ASE谱.设计将C波段ASE谱注入到掺铒光纤中作为L波段ASE谱的二次抽运源,使得L波段ASE谱功率得到了有效提高.优化光源结构参量后从两个端口分别获得了12.97 dBm和12.81 dBm的C波段和L波段ASE宽带谱.将两个输出端口组合得到了功率为15.9 dBm,泵浦转换效率达到21.6%的C+L波段超宽带ASE光源.     

110 W double-ended ytterbium-doped fiber superfluorescent source with M2 = 1.6

High-power operation of a broadband superfluorescent fiber source has been achieved via the process of amplified spontaneous emission (ASE) in a double-clad Yb-doped multimode-offset-core fiber by using a novel fiber-end termination geometry to suppress lasing. The fiber was cladding pumped by a high-power diode source at 976 nm and yielded a maximum ASE output of 63 and 47 W from the two ends of the fiber, respectively. The maximum combined ASE output was 110 W with slope efficiency with respect to launched pump power of up to 68%. The wavelength spectrum of the ASE source spanned the range from approximately 1032 to 1120 nm, and the bandwidth (FWHM) of the emission spectrum was 40 nm. The output beam was slightly multimode with a beam-quality factor (M2) of 1.6. The prospects for further improvement in performance are considered.     

一种高功率掺铒光纤超荧光光源

通过优化掺铒光纤各种参量,用一个980 nm激光二极管作抽运源,采用单程结构,在一根光纤后向获得功率高达31.74 mW(15.02 dBm)的C-波段ASE输出的同时,其前向得到了功率为10.14 mW(10.06 dBm)的L-波段ASE输出.通过简单连接组合可得到输出覆盖C＋L波段(1525~1620 nm)功率＞36 mW的掺铒光纤宽带光源.     

Theoretical and experimental study of transient response of the Yb-doped fiber amplifier

Some analysis of the transient response of the Yb-doped fiber amplifier are performed by solving a set of time-dependent rate and power transfer equations based on finite-difference method.Meanwhile,the variation of time to reach the steady state for upper level population distribution,the forward and backward amplified spontaneous emissions(ASEs)and stored energy on the system parameters including pump power,fiber length,Yb-doped concentration,and core area are numerically simulated,respectively.The results show that,by optimizing pump pulse width,stored energy can reach or even exceed the steady state value of continuous wave(CW)pump.By increasing Yb-doped concentration and core area,stored energy is increased,the ASE is suppressed and the ASE built-up time is postponed.In addition,the experimental results show the validity of the theoretical ASE built-up time.The obtained results can provide important guiding for the optimization of pump pulse width and fiber parameters.     

Effect of injection of C-band ASE on L-band erbium-doped fiber amplifier

The effect of injecting conventional band (C-band) amplified spontaneous emission on the performance of long-wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated. It uses a circulator and broadband fiber Bragg grating (FBG) to route C-band ASE from a C-band EDFA. Injection of a small amount of ASE (attenuation of 20 dB or above) improves the small signal gain with a negligible noise figure penalty compared to that of an amplifier without the ASE injection. A maximum gain improvement of 3.5 dB is obtained at an attenuation of 20 dB. At very large amounts of ASE injection (attenuation of 0 dB), the gain of the amplifier is clamped at 15.2 dB from ?40 to ?10 dBm with a gain variation of less than 0.3 dB. The saturation power is also increased from ?8 dBm (for without ASE injection) to 2 dBm (VOA=0 dB) with a slight noise figure penalty. These results show that the ASE injection technique can be used either for gain improvement or for gain clamping in L-band EDFA.     

High-power flat L-band erbium-doped fiber ASE source using dual forward-pumping scheme

We experimentally investigate a high output power L-band (1565–1605 nm) erbium-doped fiber amplified spontaneous emission (ASE) source using dual forward-pumping configuration. Such configuration allows high pumping-power operation and enhances the pumping efficiency. The high pumping efficiency of 36.1% is achieved for such ASE source with a mirror reflectance of 30%. The output power of about 72.2 mW and a linewidth of 40.8 nm with a power ripple of 0.7 dB are obtained without using any external spectral filters.     

Fabrication and amplified spontaneous emission of Eu(DBM) <Subscript>3</Subscript>Phen doped step-index polymer optical fiber

A step-index polymer optical fiber (SI POF) with a core of poly(methyl methacrylate) (PMMA) containing Eu(DBM)₃Phen has been fabricated by a preform technique. Fluorescence analysis showed that there is not obvious change in the local environment around Eu³⁺with the increase of Eu(DBM)₃Phen doping concentration. Amplified spontaneous emission (ASE) phenomenon of the doped SI POF by end-pumping with an Ar⁺-laser of 457.9 nm at ambient temperature was observed. The threshold of the pump power for the onset of ASE is found to be 120 mW for the doped SI POF with a length of 50 cm, the length is also found to be the optimal length for maximum ASE power under the input power of 200 mW. The maximum quantum conversion efficiency of the fiber is about 40%.     

126-W all-fiberized single-mode laser from an 11-μm small-core fiber

We demonstrate a 126-W all-fiberized single-mode laser from an 11-μm small-core fiber. The active fiber is a strictly single-mode fiber that produces pure single-mode. The optical to optical efficiency of the fiber laser is 68.2% with ASE suppressed by a factor of ∼35 dB and no power-roll. The output power is only limited by the available pump source, scaling the pump power may achieve much higher output power using the 11 μm small-core fiber.     

122-W high-power single-frequency MOPA fiber laser in all-fiber format

We demonstrate a high-power single-frequency master oscillator power amplifier (MOPA) fiber laser.The central wavelength of the single-frequency fiber laser seed is 1 063.8 nm,with a linewidth narrower than 20 kHz and output power of 120 mW.By using two-stage amplification,a single-frequency fiber laser with an output power of 122 W is obtained,and the optical-optical conversion efficiency is 72%.No significant amplified spontaneous emission (ASE) or stimulated Brillouin scattering (SBS) is observed.The output power can be further increased by launching more pump power.