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本文从理论和实验上研究了具有环状耦合、工作在稳定腔边缘的凹-凸型高功率激光稳定腔.在一台大激活体积万瓦级模流CO_2激光器上进行实验,获得了具有良好方向性的均匀的环状分布近场花样的7kw激光输出. 相似文献
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从菲涅尔-基尔霍夫衍射积分公式出发,运用边界元法数值计算了平凹腔平面镜均匀反射率时倾斜和未倾斜情况下基模的场强分布、相位分布和本征值,同时与高斯反射率平面镜在腔镜倾斜时的情况做了比较。研究表明,腔镜倾斜使激光场模式分布沿发生倾斜的方向向镜边缘偏移,而且在腔镜倾斜较严重时模式分布发生畸变,不再是对称的高斯分布,基模本征值随倾斜角增大而变小,光束远场分布变差。同等条件下,高斯反射率平凹腔腔镜倾斜对谐振腔引起的模畸变小于均匀反射率平凹腔,且基模光场及本征值随镜倾斜的变化关系稍不同于均匀反射率平凹腔。 相似文献
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针对异面腔四频差动激光陀螺(DILAG)工作模式不确定性和跳模对其性能的负面影响,提出了根据开机时腔体温度快速选择最优初始模的智能选模方法。分析了纵模阶数对DILAG的零偏和比例因子的影响以及跳模的危害,指出选择最优初始模是在现有基础上进一步提高DILAG性能的重要方法。通过温度实验做出了最优模相应的压电换能器(PZT)驱动电压随温度的变化曲线,为建立选模模型提供了基本依据。实验表明,智能选模使腔长控制系统加电后能快速稳定在最优初始模,减小了跳模几率,提高了腔长控制电路的鲁棒性和自适应性,对改善DILAG的性能、可靠性具有实用价值。 相似文献
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为了提高光束质量、压缩光束发散角,利用现有高功率稳定腔TEA CO2激光器进行了非稳谐振腔的技术改造及激光输出试验,非稳谐振腔采用正分支虚共焦型非稳腔方案。为充分研究谐振腔结构参数及激光振荡模体积对输出能量和光束发散角的影响,共设计加工了包含4种放大率、5种模体积的20组非稳腔腔镜组合。在其它参数都相同的试验条件下,进行了非稳腔镜的单脉冲输出对比试验,得到的最大输出能量为14 J,是原平凹稳定腔的70%,而光束发散角只是原平凹稳定腔的1/4。 相似文献
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本文报导了利用自孔径选摸技术、被动锁模原理研制成的微微秒激光器,能稳定的产生微微秒持续期的激光脉冲。其实验基础是建立在平凹镜构成的稳定半共焦腔中,选择适当的费涅尔数N的衍射损耗、腔型参数、控制激光器振荡阈值等达到自孔径选模及最佳锁模,从而在无外限孔光阑的条件下,实现了稳定的TEM00模输出运转。 激光器的输出光脉冲是用~10微微秒时间分辨率的条纹相机实时测量的。 相似文献
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在高温下成形的金属,工件与模具、外界环境之间存在剧烈的热交换,同时塑性变形功及摩擦消耗功又转化成热能,这些都引起变形体内温度的急剧变化。在金属塑性成形过程中,当温度和应变速率对材料的屈服流动应力产生明显影响时,或高温下成形的金属,应力与应变关系必须采用粘塑性本构模型。采用热力耦合粘弹塑性模型对厚壁球壳的热拉伸成形过程进行了分析,模型如图1所示。毛坯材料为LD10锻件,凸、凹模材料用5CrNnMo,材料加热温度为470℃,并经过充分保温,凸、凹模初始温度均为120℃。润滑采用油基石墨, 相似文献
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The influence of spatial saturation modulation of both the amplifier and absorber in a laser with a Fabry-Perot resonator, and of the associated Bragg-reflection, on the frequency-dependent losses necessary for single-frequency operation, as well as on the frequency synchronization of three modes, has been examined. Conditions for mode selection and mode synchronization are given. To achieve single-frequency operation in a laser with a Fabry-Perot resonator the loss difference between the mode to be selected and modes to be quenched has to be proportional to the Bragg losses of the selected mode suffered by its self-induced grating. The proportionality factor depends on the length and position of the amplifier in the cavity. In the case of a short amplifier and a short absorber inside the resonator, the discussion of conditions for synchronization of three modes shows that the synchronization regime is also determined by the position of the absorber. 相似文献
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J. J. Barroso R. A. Correa 《International Journal of Infrared and Millimeter Waves》1991,12(7):717-728
To provide the required mode selectivity for a megawatt 280 GHz gyrotron, a coaxial resonator operating in a high order TE mode is considered. Mode discrimination is achieved both by exploring the differences in the transverse structures of the competing modes and investigating a suitable geometry for the coaxial insert. For modes with close eigenfrequencies the associated diffractionQ factors can be widely different in value, thereby ensuring an effective mode selection. In the resonator studied here, the frequency separation between the design mode TE26,10,1 and its nearest competing mode TE20,12,1 is about 0.6% and the ratio of the correspondingQ factors is as high as 6.5. Unlike the coaxial resonator, in the hollow cavity without the inner conductor the fundamental spectrum of eigenfrequencies is more dense, and all TE modes within the frequency interval 271–288 GHz have approximately the sameQ factor. 相似文献
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《中国物理 B》2019,(2)
The vectorial eigenvector method was applied to compute the cylindrical vector(CV) modes of polarization-dependent resonators and multiple modes in the CV mode selected resonator were tracked. Then, the mode characteristics of CV mode selected resonator depending on the Fresnel number, geometry parameters, and polarization parameters were simulated.When the difference in reflection coefficient between radial and azimuthal polarization is greater than 0.021 for spherical semi-confocal cavity, the radially polarized TM01*mode most probably appears in the resonator due to its lowest loss,which is consistent with an azimuthal polarization-selective resonant cavity. Moreover, the appropriate phase shift factor contributes to suppress non-rotationally symmetrical modes, which promotes the selection of CV modes. The Fresnel number between 2 and 2.5 are the appropriate range of values when the value of geometry parameters g2 is 0.5, both of which decide the effective Fresnel number. 相似文献
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The possibility of use of ordinary short-focus lenses with strong spherical aberration for mode selection in a laser resonator is demonstrated. Plano-convex spherical lenses with foci from 2.5 to 10.0 cm placed inside the resonator of the CW laser diode pumped Yb:YAG laser were used to select circular modes of Laguerre-Gauss and Bessel-Gauss type, or to get ring-like, multi-mode off-axis oscillations with variable inner and outer diameters of rings. At the constant pump power mode selection was obtained by shifting an intracavity lens along the resonator axis relative to the Yb:YAG ceramics active element of 1.1 mm thickness. Peaked and hollow multi-ring beams with output power up to 30 mW were produced. Near diffraction free (ndf) propagation of the central part (minimum or maximum) of these beams was observed along distances over 10 m from the resonator output coupler. The mechanisms of mode selection due to spherical aberration in the resonator and ndf propagation of output beams are considered. The possibility of producing radially polarized beams from the laser with an intracavity lens and possible applications of the devised laser scheme are discussed. 相似文献
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Bessel-Gauss resonator with internal amplitude filter 总被引:1,自引:0,他引:1
We investigate a conventional resonator configuration, using only spherical curvature optical elements, for the generation of Bessel-Gauss beams. This is achieved through the deployment of a suitable amplitude filter at a Fourier plane create by careful selection of the geometric cavity parameters, such as mirror curvatures and resonator length. We analyze the loss behaviour of the odd and even modes, and show that the lowest Bessel-Gauss mode does not necessarily have the lowest loss. 相似文献
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R. J. Temkin 《International Journal of Infrared and Millimeter Waves》1981,2(4):629-650
An analytic theory has been derived for determining the eigenfrequencies, RF-field distribution and Q of the TEmpq modes of a gyrotron resonator consisting of a circular cylinder joined to a slowly tapered section. Explicit results are obtained for a linear taper. The cavity modes are found to have an RF-field distribution which is useful for prebunching the electron beam and enhancing efficiency. For high Q cavities, the cavity Q depends on axial mode number q as q–2, which is important for mode discrimination. Proper selection of taper length is found to reduce the Q of high q modes, also aiding in mode discrimination. The present approach may be applied to other forms of weakly irregular cavities, such as cavities with nonlinear tapers.Work supported by U.S.D.O.E. Contract DE-AC02-78ET-51013Supported by U.S. Department of Energy 相似文献
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M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
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E. J. Curtis P. G. Frayne 《International Journal of Infrared and Millimeter Waves》1992,13(6):815-824
The simultaneous excitation of the fundamental and higher order radial modes in a degenerate confocal resonator leads to destructive interference between modes on the optic axis and hence reduces the power coupled by an axial iris. This mode competition may be reduced drastically by proper control of the aperture flux distribution and is of particular significance when the resonator is used for the power combining of solid-state sources. 相似文献
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激光晶体由于吸收了一部分泵浦光能量,产生的热量引起晶体内温度不均匀分布,使晶体内的折射率产生不均匀分布,对振荡光产生相应的相位调制,引起振荡光光场再分布,进而导致振荡光模式发生变化。谐振腔具有滤波作用,谐振腔会过滤掉振荡光中与谐振腔不匹配的模式,引起损耗,用MATLAB模拟晶体内温度场分布,通过计算谐振腔内基模的热致损耗及低阶模转换到高阶模的比例,并研究谐振腔中各阶模式的转换问题,为抑制高阶模并减小损耗提供理论依据。 相似文献
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We report on realization of an efficient triply resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyperparametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb by observing the modulation of the light escaping the resonator. 相似文献