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。     

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.     

Tapered fiber amplifier with high gain and output power

We present a high-power ytterbium fiber amplifier based on active tapered double-clad fiber (T-DCF) and capable of high single-pass gain. The T-DCF power amplifier seeded with a 320 mW narrow-band signal generates up to 110 W of average output power corresponding to more than 25 dB gain. The amplifier exhibits near-diffraction-limited beam quality (M ² = 1.06) at the highest output power, which was limited by the available pump power. With a broadband seed source, the amplifier produced a gain of nearly 40 dB obtained for low-signal limit of the seed. The high output power combined with high gain is achieved owing to amplified spontaneous emission (ASE) filtering and increased stimulated Brillouin scattering (SBS) threshold inherent to the axially non-uniform geometry. The amplifier operates efficiently with a wide range of input seed powers thus providing the basis for one-stage tapered amplifier which combines the functions of preamplifier and power amplifier and can be a competitive alternative to multi-stage design.     

Low noise gain-clamped L-band erbium-doped fiber amplifier by utilizing fiber Bragg grating

A novel gain-clamped long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is proposedand experimented by using a fiber Bragg grating (FBG) at the input end of the amplifier. This designprovides a good gain clamping and decreases noise effectively. It uses two sections of erbium-doped fiber(EDF) pumped by a 1480-nm laser diode (LD) for higher efficiency and lower noise figure (NF). The gainis clamped at 23 dB with a variation of 0.5 dB from input signal power of -30 to -8 dBm for 1589 nm andNF below 5 dB is obtained. At the longer wavelength in L-band higher gain is also obtained and the gainis clamped at 16 dB for 1614 nm effectively. Because the FBG injects a portion of backward amplifiedspontaneous emission (ASE) back into the system, the gain enhances 5 dB with inputting small signal.     

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.     

Amplification enhancement of L-band erbium-doped fiber amplifiers by reflection scheme

A reflection L-band erbium-doped fiber amplifier (EDFA), which can effectively suppress and completely exploit the backward C-band amplified spontaneous emission (ASE) with a feedback reflection loop, is presented in this paper. The mechanism of the backward ASE secondary pumping effect is experimentally investigated in detail. Our experimental results have shown that, for a given input pump power, compared to the end-pumped EDFA, the gain and output power of the reflection EDFA can be improved considerably without paying much noise penalty. When the EDFA operates with flattened gain spectra, the gain is improved by about 7 dB with an extra noise penalty of about 1.2 dB, where the saturation output power is increased by 2.5–3.2 dB and which may also be made independent of the input signal power.     

Ultra-broadband amplified spontaneous emission source by using heterogeneous optical amplifier

In this work, we propose and experimentally investigate an ultra-broadband amplified spontaneous emission (ASE) light source with 113.8 nm bandwidth (1446.2 to 1560.0 nm) by using a cascaded two-stage optical amplifier, which is consisted of semiconductor optical amplifier (SOA, 1st stage) and erbiumdoped fiber amplifier (EDFA, 2nd stage), when the output intensity is above ?35 dBm/0.01 nm. And, the EDFA only uses a 3 m long erbium-doped fiber (EDF) with a 27 mW pumping power and SOA is driven at 200 mA bias current. Moreover, the proposed amplifier also can provide a broadband gain amplification of 114 nm in the wavelengths of 1464.0 and 1578.0 nm with the noise figure distribution of 6.8 to 8.1 dB.     

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.     

2μm single-frequency master-oscillator fiber power amplifier

We report a single frequency laser source consisting of a Tm:YAP coupled-cavity master-oscillator and a Tm-doped fiber power amplifier. The MOFPA yielded 4.55 W of single frequency output at 1990 nm when the input signal was 270 mW and the pumping power was 35.2 W. A strong amplification of spontaneous emission (ASE) was observed when higher pumping power was applied. Therefore, the output power of the single frequency fiber power amplifier was limited by the input power of seed laser.     

High-power, single-mode, linearly polarized, ytterbium-doped fiber superfluorescent source

High-power operation of a single-mode, linearly polarized, broadband superfluorescent fiber source has been achieved by using a two-stage cladding-pumped fiber configuration comprising a low power, single-ended, ytterbium-doped superfluorescent fiber seed source and a high-power cladding-pumped, polarization-maintaining, large-mode-area, ytterbium-doped amplifier pumped by a high-power diode source at 976 nm. The source yielded a maximum linearly polarized output of 106 W with a slope efficiency of up to 67% with respect to the launched pump power and with a measured polarization extinction ratio of 13.5 dB. The wavelength spectrum of the superfluorescent source spanned the range continuously from ~1035 to 1100 nm, and the bandwidth (FWHM) of the emission spectrum was 21 nm. The minimum seed power required for an output power over 100 W was only 10 mW, corresponding to an effective power gain in the amplifier stage of 40 dB. Single-spatial-mode operation with a beam propagation factor (M(2))<1.1 was achieved by bending the amplifier fiber to a bend radius of ~8 cm, without a significant reduction in output power.     

Gain-clamped dual-stage L-band EDFA by using backward C-band ASE

A dual-stage L-band gain-clamped erbium-doped fiber amplifier (GC-EDFA) by using backward C-band amplified spontaneous emission (ASE) is proposed. Compared with other similar GC-EDFAs, the proposed structure has higher and flatter clamped gain in L-band because of its optimal pump power and EDF length. The flatness from 1570 nm to 1600 nm arrives 0.77 dB, the bandwidth of 3 dB is more than 35 nm and the maximal input signal power arrives −15 dBm.     

100 W全光纤声光调Q光纤激光器实验研究

 报道了一台全光纤结构主振荡功率放大(MOPA)型掺镱脉冲光纤激光器,以光纤光栅为腔镜,光纤型声光调Q的光纤激光器为种子源,通过两级掺镱双包层光纤放大器实现功率放大。对声光调Q的光纤激光器输出特性进行了研究,比较了不同泵浦波长、不同重复频率对激光输出功率和脉冲宽度的影响,并实现了最短脉冲宽度25 ns、单脉冲能量45 μJ的脉冲激光输出。在重复频率50 kHz时,对脉冲宽度130 ns、平均功率0.6 W的种子光进行放大,得到了平均功率102.5 W、脉冲宽度约240 ns的激光输出。     

新颖的高功率L-波段掺铒光纤超荧光光源

研究了L-波段超荧光在光纤中的产生机理,设计了一种带光纤圈反射器的双级双程前向输出L-波段光源结构,通过对两级采用掺铒浓度不同的光纤并优化其长度及两级泵浦光功率,实验中获得了功率高达19.86mW(12.98dBm)、中心波长为1577.421nm的L-波段(1555-1620nm)超荧光光源。实现了低浓度掺铒光纤起诱导光及改善光谱的作用,高浓度光纤为主要发光源,采用光纤圈反射器提高了泵浦光的利用效率、光源的平坦度及稳定性。同时分析了结构中各个参量对光源各方面性能的影响,对光源的设计具有指导意义。     

L-band EDFA 性能与增益光纤长度关系的分析

分析和模拟L_band EDFA的增益特性对其优化设计和实验有着重要的意义。基于Giles模型,数值模拟了L_band EDFA中的信号光、泵浦光和放大自发辐射(ASE)在一定泵浦功率下与铒光纤长度的关系;分析了L_band EDFA本征增益平坦的产生机理;数值模拟了小信号增益平坦特性。结果表明,在一定的泵浦功率下,如果在所选择的L_bandEDFA中铒光纤长度合适,则不需要任何平坦化处理就可以得到比较平坦的增益谱线。     

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.     

Characteristic comparison of single-pumped L-band erbium-doped fiber amplified spontaneous emission sources

We experimentally investigate the single-pumped L-band (1570–1610 nm) erbium-doped fiber amplified spontaneous emission (ASE) source in four configurations with single-pass forward, single-pass backward, double-pass forward (DPF), and double-pass backward structures. The characteristics are examined and compared in terms of the output power, mean wavelength, spectral linewidth, and pumping conversion efficiency. Among them, only DPF configuration is satisfied, and other configurations are intrinsically hard to be an L-band ASE source for applications. Such results are significantly different as compared with their corresponding C-band counterparts.     

980-nm all-fiber mode-locked Yb-doped phosphate fiber oscillator based on semiconductor saturable absorber mirror and its amplifier

A 980-nm semiconductor saturable absorber mirror(SESAM) mode-locked Yb-doped phosphate fiber laser is demonstrated by using an all-fiber linear cavity configuration. Two different kinds of cavity lengths are introduced into the oscillator to obtain a robust and stable mode-locked seed source. When the cavity length is chosen to be 6 m, the oscillator generates an average output power of 3.5 m W and a pulse width of 76.27 ps with a repetition rate of 17.08 MHz. As the cavity length is optimized to short, 4.4-m W maximum output power and 61.15-ps pulse width are produced at a repetition rate of 20.96 MHz. The output spectrum is centered at 980 nm with a narrow spectral bandwidth of 0.13 nm. In the experiment, no undesired amplified spontaneous emission(ASE) nor harmful oscillation around 1030 nm is observed. Moreover,through a two-stage all-fiber-integrated amplifier, an output power of 740 m W is generated with a pulse width of 200 ps.     

Wavelength tunable erbium-doped fiber ring laser operating in L-band

We describe a novel erbium-doped fiber ring laser utilizing the backward amplified spontaneous emission (ASE) power as a secondary pump source so that it can operate in L-band stably. The output wavelength can be tuned in a wide range of 45 nm, from 1560 to 1605 nm. We also compared this scheme with the condition of not using the ASE as secondary pump source, and found this scheme could improve the performance of the laser when using the same components.     

基于多波长类噪声脉冲的掺铒光纤激光器

报道了一种基于多波长类噪声脉冲的被动锁模掺铒光纤激光器。采用980 nm半导体激光器作为泵浦源，2.5 m长的掺铒光纤作为增益介质。锁模机制为非线性放大环形镜(NALM)。通过自相关迹证明输出脉冲为类噪声脉冲。该类噪声脉冲的光谱3 dB带宽可达17.2 nm，边模抑制比为47.7 dB，重复频率为5.434 MHz，单脉冲能量为7.9 nJ。为了实现平坦的多波长输出，在NALM结构中加入Sagnac环干涉仪，获得了最大波长数为5的平坦多波长类噪声脉冲，平坦度为1.995。