Seeded erbium/ytterbium codoped fibre amplifier source with 87 W of single-frequency output power

A highly efficient cladding-pumped erbium/ytterbium-doped large-core fibre amplifier, generating up to 87 W of single-frequency continuous-wave output at 1563 nm, with a good beam quality (M/sup 2//spl les/1.7), in a master oscillator power amplifier configuration is reported. The overall optical power conversion efficiency was 26%.     

发展中的LD抽运调Q铒玻璃激光器

介绍了二极管抽运调Q铒玻璃激光器的发展过程、发展水平和发展趋势,主要包括:铒玻璃激光材料、调Q技术、抽运系统。铒玻璃材料向高离子掺杂浓度方向发展;双侧面对称抽运方式可以提高抽运效率的同时还可以减少材料的热畸变;Co2+:MgAIO4晶体发展为最合适的被动调Q材料;激光器高重频运转需要精确的温度控制。最后,探讨了该课题进一步发展要解决的问题。     

Broadband tunable single frequency diode-pumped erbium doped fibre laser

A single frequency erbium fibre laser with continuous wavelength tuning over the range 1525-68 nm has been demonstrated using a unidirectional loop mirror (ULM) configuration. The fibre laser is diode pumped at 1480 nm with a threshold of 9 mW, slope efficiency of 12% and has a linewidth of less than 295 kHz.<>     

230-mW diode-pumped single-frequency Er:Yb laser at 1.5 μm

We report on a diode-pumped Er:Yb laser able to generate a single-frequency output power in excess of 200 mW at both 1.53 μm and 1.56 μm and over 300 mW in multimode operation. The tuning characteristics of the source are reported and discussed. The relative intensity noise presents in all configurations a peak value lower than -92 dB/Hz and its level decreases below -160 dB/Hz for frequencies higher than 8 MHz     

Theoretical study on erbium ytterbium co-doped super-fluorescent fiber source

Erbium ytterbium co-doped super-fluorescent fiber source (EYD-SFS) has been simulated by a theoretical model based on rate equations and power transfer equations. The output performances of four basic structures of EYD-SFS have been expressed, and it indicated that the DPF structure is a preferable structure. The dependence of output power, mean wavelength and bandwidth stability on the pump fiber length and the concentration of Er³⁺ and Yb³⁺ have also been studied. The results indicated with a proper doping concentration of Er³⁺ and Yb³⁺ of 6.0×10²⁶ ions/m³ and 1.0×10²⁷ ions/m³, the optimal gain fiber length is 3.6 cm. In this condition, good performances of DPF structure of EYD-SFS have been achieved.     

Thermal lensing in diode-pumped ytterbium Lasers-Part I: theoretical analysis and wavefront measurements

A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. In this first part, we focus on theoretical considerations and we describe an original technique suitable for thermal lensing measurements in end-pumped materials. We first derive an expression of the temperature distribution with account of absorption saturation and pump beam divergence inside the crystal, and we address a more general discussion on the particularities of quasi-three-level lasers, as far as thermal effects and fracture issues are concerned. The thermal lens was then measured using a simple technique based on a Shack-Hartmann wavefront analyzer, under lasing and nonlasing conditions. We demonstrate that the technique allows precise wavefront measurements even on small spots. Thermal lensing measurements are finally presented in Yb-doped YAG, GGG, YCOB, GdCOB, KGW, and YSO crystals.     

Intensity noise in diode-pumped single-frequency Nd:YAG lasers andits control by electronic feedback

The power spectrum of the relative intensity noise (RIN) of single-frequency diode-pumped Nd:YAG lasers is observed to be shot-noise limited at frequencies above 20 MHz for a photocurrent of up to 4.4 mA. Relaxation oscillations result in noise 60-70 dB above shot noise at a few hundred kilohertz. These relaxation oscillations have been suppressed using electronic feedback     

+21 dBm erbium power amplifier pumped by a diode-pumped Nd:YAGlaser

Efficient energy transfer has been demonstrated in an Er/Yb codoped phosphorus-doped silica fiber for the first time. This has indirectly allowed the use of reliable, high-power AlGaAs diode laser arrays as the semiconductor pump source through the use of a diode-pumped Nd:YAG laser (DPL) operating at 1064 nm. Small signal gains of 42 dB and output powers of 71 mW (+18.5 dBm) have been observed with a single DPL. Bidirectional pumping with two DPLs has yielded an output power of 130 mW (+21 dBm)     

Thermal lensing in diode-pumped ytterbium Lasers-Part II: evaluation of quantum efficiencies and thermo-optic coefficients

A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. This papers follows the presentation of theoretical considerations and experimental wavefront measurements, which have been the subject of Part I. In this paper, we study the evolution of thermal lensing versus absorbed pump power, and we derive two parameters valuable for laser design and power scaling. The quantum efficiency and the thermo-optic coefficient, in Yb-doped YAG, GGG, GdCOB, YCOB, KGW and YSO. The clear difference between thermal lensing under lasing and nonlasing conditions is the proof that nonradiative effects occur in all the crystals under investigation. An analytical model which takes into account the laser extraction efficiency enables to explain all the experimental features and allows to infer the fluorescence quantum efficiency of the samples (in the range 0.7-0.96). Under nonlasing conditions, the thermal lens dioptric power experiences a roll-off, for which we propose an explanation based on the theory presented in Part I. These results are then used to yield the thermo-optic coefficient of the crystals. At last, we propose a simple analytical formulation useful for a rough estimation of the focal length.     

Field demonstration of coherent transmission system with diode-pumped erbium doped fibre amplifiers

Reports a field demonstration of 622 Mbit/s DPSK and FSK coherent transmission over 200 km of installed single mode fibre. Diode-pumped erbium doped fibre amplifiers were used as both power amplifiers and repeaters. System loss budgets of more than 68 dB were achieved with an intermediate amplifier repeater gain of 16.5 dB. Both systems incorporated fully automated endless polarisation control.<>     

LD泵浦铒镱共掺磷酸盐玻璃被动调Q微型激光器实验研究

1.5 m LD泵浦铒玻璃被动调Q微型激光器是目前军事激光测距的研究热门,获得较高的激光单脉冲能量尤为重要。对以波长为940 nm的二极管激光器作为泵浦源,Er3+/Yb3+共掺磷酸盐玻璃作为增益介质,Co2+:MgAl2O4作为调Q晶体的微型化激光器进行了实验研究。为获得LD抽运铒镱共掺磷酸盐玻璃被动调Q微型激光器的最佳能量输出条件,分析了影响LD泵浦被动调Q激光器输出单脉冲能量的因素,并对影响被动调Q微型激光器输出能量的泵浦条件,增益介质长度,输出镜反射率等参数进行了多组实验优化,最终获得了波长1.535 m,单脉冲能量113 J,脉宽6 ns,重复频率10 Hz,光束质量为1.2的稳定人眼安全激光输出。     

铒镱共掺铋磷酸盐玻璃光谱性能的研究

基于光通信技术发展对光放大器材料的带宽要求,研究了掺铒铋磷酸盐玻璃的结构、熔制性能,以及其光谱性能,并且用Judd-Ofelt理论进行了光谱计算分析。得到了一种以铋磷酸盐为基质的光放大器玻璃材料,其折射率为1.778,荧光半峰全宽为54nm,发射截面为0.61×10-20cm2,其荧光寿命达到了8ms。结果表明,铒镱共掺铋磷酸盐玻璃是一种良好的宽带放大器材料。     

Observation of dual relaxation-oscillations and their dynamics inall-PM erbium/ytterbium fibre ring-lasers

The authors report experimental observation of dual relaxation-oscillations and their dynamical behaviour that occurs in all-PM Er/Yb fibre ring-lasers. The dual relaxation-oscillations are the results of unambiguous two orthogonal-polarisation modes that exist in an all-PM cavity. Varying the initial cavity conditions controls the dynamical behaviour between the two relaxation-oscillations. A simple model was used to simulate the experimental results, which are in good agreement with the observed results     

溶胶凝胶法制备Yb3+/Er3+共掺氧化铝材料的光谱性质

为了得到更加有效的掺饵光波导放大器材料,采用改进了激活剂掺入途径的溶胶凝胶方法,制作了不同比例Yb3+Er3+共掺杂的γ相氧化铝粉体材料方法,测量了样品的吸收和光致发射光谱并进行了分析.结果表明,Yb3+离子的掺入能很大地提高样品对980nm左右激发光的吸收效率,Er3+离子1534nm主发射峰的发射强度最大增加了约6.3倍;体系中Yb3+:Er3+的掺杂存在最佳比例,最佳掺杂比例约为6:1;同时X射线衍射法测试表明,最佳的热处理温度为900℃,相同的热处理温度下,Yb3+的掺入能延缓Al2O3由无定形相向γ相转变的过程,这一结果对进一步改善掺饵光波导放大器的特性是有帮助的.     

Efficient diode-pumped CW and Q-switched single-mode fibre laser

We report the efficient operation an Nd3+-doped silica single-mode fibre laser pumped by a GaAlAs laser diode. A CW output power in excess of 1 mW at 1.088 ?m has been obtained with a slope efficiency of 33%. Q-switched operation of this device is also reported.     

The route toward a diode-pumped 1-W erbium 3-μm fiber laser

A rate-equation analysis of the erbium 3-μm ZBLAN fiber laser is performed. The computer calculation includes the longitudinal spatial resolution of the host material. It considers ground-state bleaching, excited-state absorption (ESA), interionic processes, lifetime quenching by co-doping, and stimulated emission at 2.7 μm and 850 mn. State-of-the-art technology including double-clad diode pumping is assumed in the calculation. Pump ESA is identified as the major problem of this laser. With high Er³⁺ concentration, suitable Pr³⁺ co-doping, and low pump density, ESA is avoided and a diode-pumped erbium 3-μm ZBLAN laser is predicted which is capable of emitting a transversely single-mode output power of 1.0 W when pumped with 7-W incident power at 800 nm. The corresponding output intensity which is relevant for surgical applications will be in the range of 1.8 MW/cm². Compared to Ti:sapphire-pumped cascade-lasing regimes, the proposed approach represents a strong decrease of the requirements on mirror coatings, cavity alignment, and especially pump intensity. Of the possible drawbacks investigated in the simulation, only insufficient lifetime quenching is found to have a significant influence on laser performance     

Theoretical analysis of the dynamic behavior of highly-efficient erbium/ytterbium codoped fiber lasers

A numerical study of the transient behavior of single-mode Er/sup 3+//Yb/sup 3+/ codoped fiber lasers is presented. The model, based on propagation-rate equations, includes both uniform up-conversion from the /sup 4/I/sub 15/2/ and /sup 4/I/sub 9/2/ erbium levels and the pair-induced energy transfer process from ytterbium to erbium. We show that neglecting the r dependence of the operating fiber laser parameters allows accurate simulation results at minimum numerical effort. Using this numerical model, we characterize the laser relaxation oscillations and the effect of ytterbium on the dynamic behavior and stability with respect to fluctuations of the pump power. Our results confirm that the presence of Yb/sup 3+/ enhances the efficiency of the laser and show that its stability is also significantly improved.     

Efficient wavelength conversion with high-power passivelyQ-switched diode-pumped neodymium lasers

Powerful CW diode-pumped Nd:YAG and Nd:YVO4 lasers Q-switched by Cr:YAG saturable absorbers demonstrate efficient (30%-60%) harmonic and parametric conversion, generating hundreds of milliwatts from ultraviolet to mid-infrared     

波长可切换窄线宽单频掺镱光纤激光器（特邀）

基于光纤环形激光器,设计出由三端口环形器、偏振控制器、未泵浦保偏掺镱光纤和光纤布拉格光栅组成的滤波器件作为高精度滤波器对谐振腔内的模式个数进行抑制,通过调谐偏振控制器,在保偏掺镱光纤内形成的梳状光谱和动态光栅,实现了窄线宽、单、双波长可切换单频掺镱光纤激光器。单波长运行时,在1064.37 nm处测得激光器输出线宽346 Hz,光信噪比大于50 dB,30 min内该激光器波长及功率的不稳定性均在0.01 nm和0.2 dB范围内。通过调节偏振控制器,单波长和双波长可以实现互相切换,双波长分别位于1064.156 nm和1065.236 nm。该技术为超窄线宽激光器的双波长输出提供了新的途径。     

Long span coherent transmission with erbium ytterbium doped fibre power amplifier over a 70 dB loss budget

A combination of a high power Er/Yb fibre optic amplifier and a coherent transmission system are used to achieve very large optical link loss budgets of 70 dB at 167 Mbit/s and 67 dB at 622 Mbit/s. A transmit power of +18.2 dBm was launched into low loss optical fibre without evidence of stimulated Brillouin scattering.<>