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The propagation performance of high-power partially coherent fibre laser beams in a real environment is investigated and the theoretical model of a high-power fibre laser propagating in a real environment is established. The influence of a collimating system and thermal blooming is considered together with atmospheric turbulence and mechanical jitter. The laser energy concentration of partially coherent beams in the far field is calculated and analysed based on the theoretical model. It is shown that the propagation performance of partially coherent beams depends on the collimating system, atmospheric turbulence, mechanical jitter and thermal blooming. The propagation performance of partially coherent beams and fully coherent beams is studied and the results show that partially coherent beams are less sensitive to the influence of thermal blooming, which results in that the energy degeneration for partially coherent beams is only 50% of that for fully coherent beams. Both partially coherent beams and fully coherent beams become less sensitive to thermal blooming when the average structural constant of the refraction index fluctuations increases to 1.7 × 10-14 m-2/3. The investigation presents a reference for applications of a high-power fibre laser system. 相似文献
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介绍了大气湍流效应和热晕效应对列阵合成激光传输特性和光束质量影响的理论研究进展。主要介绍了合成激光在大气中传输的解析和数值模拟研究方法,大气湍流效应对列阵合成光束的光强分布、远场发散角、方向性、曲率半径和湍流距离的影响,以及大气热晕效应对列阵合成光束的光强分布、传输效率、重心偏移、热晕时间尺度和焦移的影响。研究结果表明,大气湍流效应和热晕效应对合成激光光束质量的影响与光束合成方式、合成光束参数以及大气参数密切相关。 相似文献
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Based on the one-aerosol model, we investigate the influence of thermal blooming on the propagation of solid-state heat-capacity
laser (SSHCL) beams in atmosphere. By employing only this aerosol model and ignoring the diffraction and atmospheric turbulence,
we evaluate the change in the average transmittance when the incident intensity and the propagation distance are changed.
We conclude that the effect of thermal blooming on the propagation of SSHCL beams in the atmosphere is dependent on the incident
intensity and the propagation distance. As the incident intensity and propagation distance increase, the influence of thermal
blooming on the average transmittance strengthens. However, when the incident intensity is not strong enough, the incident
intensity barely affects the average transmittance.
PACS 42.65.Jx; 42.55.Rz; 42.68.Ay; 42.68.Jg 相似文献
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Various factors that can effect thermal blooming in stagnation zone situations are examined, including stagnation-zone motion,
longitudinal air motion in the neighborhood of the stagnation zone, and the effects of scenario noncoplanarity. Of these effects,
only the last offers reasonable hope of reducing the strong thermal blooming that normally accompanies stagnation zones; in
particular, noncoplanarity should benefit multipulse more than cw beams. The methods of treating nonhorizontal winds hydrodynamically
for cw and multipulse steady-state sources are discussed. Aspects of pulse “self-blooming” are also considered.
Work was performed under the auspices of the U. S. Energy Research and Development Administration under contract W-7405-Eng-48,
U. S. Navy Contract N00014-76-F-0017 and U. S. Army Contract W31U31-73-8543. 相似文献
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从小尺度热晕线性理论出发,在non-Kolmogorov谱的基础上,得到了non-Kolmogorov谱湍流下热晕相位补偿的Strehl比表达式,分析了湍流谱对高能激光的相位补偿的影响.研究结果表明湍流谱对湍流热晕效应的相位补偿有重要的影响.在相同的湍流菲涅耳数下,当谱指数越接近于3时补偿效果越差,谱指数接近于4时补偿效果越好.在相同大气相干长度条件下或在相同湍流折射率常量条件下,当谱指数接近于3时,Strehl比随热晕效应的增强而下降变快,当湍流谱指数逐渐接近于4时,Strehl比下降速度变慢.其原因是随着湍流谱指数的增大,湍流热晕相互作用引起的对数振幅起伏增长变慢. 相似文献
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考虑到大气中吸收系数随高度变化,通过内插法得到不同大气模型一定高度下大气的吸收系数,建立序列脉冲激光在地对空垂直传输的热晕模型。通过数值计算方法分析风场渡越时间内脉冲数为2时的序列脉冲在中纬度地区夏季和冬季、热带地区、近北极地区夏季和冬季5种大气模型下的热晕效应。结果表明:当光束孔径为0.25 m,初始功率为200 kW,波形为高斯状的激光束在近北极冬季传输10 km后沿横轴方向光强峰值偏移0.056 9 m,而热带光强峰值强度偏移最远为0.224 m,为近北极冬季时的4倍;脉冲激光在热带传输10 km后的靶面功率仅为15.06 kW,近北极冬季靶面功率为热带的10.5倍。热带地区的热晕效应最明显,中纬度地区次之,近北极地区最弱。激光在夏季传输要比冬季传输的热晕效应严重,而且近北极地区夏季要比中纬度地区冬季的热晕效应更严重。 相似文献
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We consider the propagation of super-Gaussian monochromatic laser beams in a three-dimensional array of quantum dots coupled
by the tunneling effect along one axis. The electron energy spectrum of the system corresponds to the Hubbard model, where
the Coulomb interaction of electrons in quantum dots is taken into account. The field of the laser beam is described by the
Maxwell equations, from which a nonhomogeneous wave equation for the vector potential is obtained. In the approximation of
slowly varying amplitudes and phases, the wave equation is reduced to a phenomenological equation describing the electromagnetic
field in an array of chains of quantum dots. We study the influence of the system parameters and the frequency of the laser-beam
field on the propagation in the medium by solving numerically the phenomenological equation. We obtain the dependence of the
factor characterizing the diffraction blooming of the beam in an array of chains of quantum dots on the parameters of the
system’s electron energy spectrum. 相似文献
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Joachim Piprek 《Optical and Quantum Electronics》2013,45(7):581-588
High-power broad-area laser diodes often suffer from a widening of the lateral (slow axis) far-field with increasing current, called thermal blooming, which is mainly caused by the non-uniform self-heating of the laser and has been studied for several decades. This paper presents the first self-consistent electro-thermal-optical simulation and analysis of such thermal blooming. Using a real InGaAs/GaAs broad-area laser as an example, a 900A/cm2 higher current density is shown to lead to only 0.5K stronger lateral temperature drop inside the ridge waveguide but to a one degree wider slow axis far field. Small non-thermal blooming is also observed. 相似文献
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激光大气传输中热晕的数值模拟 总被引:23,自引:6,他引:17
采用快速傅里叶变换,研究了激光在大气传输中的热晕现象。得出了一定条件下,热晕随激光输入功率和传播距离的稳态变化规律,并计算了激光在大气中传输10km时发生热晕的功率阈值。在瞬态情况下,研究了有风和无风热晕现象。 相似文献
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We investigate the effects of wind directions on the thermal blooming of a laser beam propagating in the air. We calculate the distributions and contours of the laser intensity for different wind directions and find that the thermal blooming for the laser propagating in the down-wind direction is weaker than that of the up-wind case. 相似文献
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Theoretical and experimental studies on high-power laser-induced thermal blooming effect in chamber with different gases
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Xiangyizheng Wu 《中国物理 B》2022,31(8):86105-086105
High-power laser induced thermal blooming effects in a closed chamber with three different gases are investigated theoretically and experimentally in this work. In the theoretical treatment, an incompressible gas turbulent model is adopted. In the numerical simulation the gas refractive index as a function of both the temperature and pressure is taken into consideration. In the experimental study the pump-probe technology is adopted. A high-power 1064-nm fiber laser with maximum output power of 12 kW is used to drive the gas thermal blooming, and a 50-mW high-beam-quality 637-nm laser diode (LD) is used as a probe beam. The influences of the gas thermal blooming in the chamber on the probe beam wavefront and beam quality are analyzed for three different gases of air, nitrogen, and helium, respectively. The results indicate that nitrogen is well suitable for restraining thermal blooming effect for high-power laser. The measured data are in good agreement with the simulated results. 相似文献
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A dynamic electronic speckle pattern interferometry (ESPI) method was applied to study the blooming process in two kinds of flowers, the lily and the tulip. The complicated displacement fields of the flower petals were precisely monitored throughout the entire blooming process. The optical setup is a Fizeau type interferometer with relatively high robustness to air turbulence and vibrations. For quantitative evaluation of the displacement field, the subtraction-addition method (SAM), which utilizes only the digital signal processing of a sequence of images, was implemented. Measurements with accuracy in the range of λ/10 were achieved. 相似文献
20.
In this paper, we investigate the effect of the wind speed on the thermal blooming of a laser beam propagating in the rain. In view of simulations, we obtain the contour distribution of the laser beam and calculate the change in air density by changing the wind speed for different rain rates. We find that with increase in the rain rate, the effect of the wind speed on the thermal blooming enhances. 相似文献