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根据菲涅耳衍射积分,研究了拉盖尔-高斯光束经过单缝衍射后的光强分布,发现拉盖尔-高斯光束经过单缝后衍射条纹会出现空心和发生弯曲,并与实验结果进行了比较.研究了拉盖尔-高斯光束经过单缝后的螺旋谱,发现单缝的存在会使螺旋谱展宽.给出了拉盖尔-高斯光束经过单缝衍射后的相位分布.研究结果可用于涡旋光束拓扑电荷数的测量. 相似文献
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利用有限元法,对圆形镜共焦腔的模式分布进行数值计算,结果表明:当菲涅尔数较小时,最低损耗模式为低阶模,而菲涅尔数较大时,优先起振的模式为高阶模。 相似文献
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涡旋光束单缝衍射的理论和实验研究 总被引:2,自引:1,他引:2
根据菲涅耳衍射积分,研究了拉盖尔-高斯光束经过单缝衍射后的光强分布.研究表明,拉盖尔-高斯光束经过单缝后衍射条纹会发生断层和弯曲,弯曲的方向和程度跟拓扑电荷数紧密相关.实验结果也证实了这一现象.还研究了拉盖尔-高斯光束经过单缝后的螺旋谱.研究表明,单缝的存在会使螺旋谱展宽,展宽程度受到拓扑电荷数、光斑大小以及单缝缝宽的影响. 相似文献
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以复宗量拉盖尔—高斯(ELG)光束为例,对ELG光束经硬边光阑、超高斯光阑和锯齿光阑的衍射特性作了详细的比较研究。数值计算结果表明,超高斯光阑和锯齿光阑的优点是能有效抑制菲涅尔衍射调制并有较大的填充因子。 相似文献
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涡旋波加热是目前电离层加热试验技术研究的一个热点,但主要侧重于试验现象的分析和解释,对涡旋加热波传播特性及空间场分布特性的讨论很少.文章从菲涅耳衍射理论出发,利用厄米-高斯模和拉盖尔-高斯模的相互转换关系,对电离层涡旋加热波在自由空间的传播特性进行了理论分析,推导了其解析表达式.结果表明涡旋电磁波在传播时,可保持自身表达形式的不变性.依据解析表达式,仿真分析了涡旋波空间幅相分布与拉盖尔-高斯模阶数的关系,给出了涡旋场峰值波束指向的求解方法和公式.这些结论为利用涡旋波深入开展电离层加热研究,实现可控的涡旋加热场空间分布提供了一定的理论指导. 相似文献
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为了研究受限拉盖尔-高斯光束湍流传输时轴上光强分布,采用扩展惠更斯-菲涅耳原理方法进行了理论分析,得到了受发射圆孔限制的拉盖尔-高斯光束在大气湍流中传输时轴上光强的表达式。并运用MAPLE模拟,取得了不同湍流强度、波长和发射圆孔孔径下轴上光强的分布理论数据。结果表明,拉盖尔-高斯光束在不同阶数、湍流强度、波长和发射圆孔孔径下,真空和湍流较弱时,轴上光强在近场发生明显振荡,达到最大值后,强度明显开始降低,湍流较强时,传输很近距离强度就迅速衰减,并与其在真空中的传输特性进行了比较。这一结果对研究拉盖尔一高斯光束是有帮助的。 相似文献
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为了研究受限拉盖尔-高斯光束湍流传输时轴上光强分布,采用扩展惠更斯-菲涅耳原理方法进行了理论分析,得到了受发射圆孔限制的拉盖尔-高斯光束在大气湍流中传输时轴上光强的表达式.并运用MAPLE模拟,取得了不同湍流强度、波长和发射圆孔孔径下轴上光强的分布理论数据.结果表明,拉盖尔-高斯光束在不同阶数、湍流强度、波长和发射圆孔孔径下,真空和湍流较弱时,轴上光强在近场发生明显振荡,达到最大值后,强度明显开始降低,湍流较强时,传输很近距离强度就迅速衰减,并与其在真空中的传输特性进行了比较.这一结果对研究拉盖尔-高斯光束是有帮助的. 相似文献
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An iteration technique is used for a theoretical study of the field distributions and diffraction losses at the reflectors of an asymmetric confocal cylindrical resonator having an output hole in one mirror for the low-loss TEM00 and TEM10 modes with Fresnel numbers ofN = 0.8 and 1.2. A digital computer is used to numerically iterate an initially launched uniform distribution as it reflects back and forth between the mirrors until a steady-state field distribution occurs. The edge and coupling hole diffraction losses and the power coupled from an output hole in one mirror are also computed. The presence of the coupling hole produces a perturbation of the field distribution with distortion of the field increasing for increasing Fresnel number and for low-order modes. The relationship between hole radius and power output is presented. An optimum-size coupling hole may be selected from this data, which will yield maximum power output in the mode of operation desired. It has been found that, with the use of a coupling hole, mode selection of the lowest order TEM00 mode is possible for resonators having large Fresnel numbers (N > 1.0 ). 相似文献
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模式失配对连续波腔衰荡技术测量的影响 总被引:1,自引:1,他引:1
对连续波腔衰荡技术中的模式失配对测量结果的影响进行了理论分析和实验研究。在腔菲涅耳数较大时,基于高斯光束的参数q变换规律及模式耦合有关理论,分析和模拟了引起模式失配的两个主要因素——光束半径失配和相前曲率失配对一般稳定腔连续波腔衰荡法测量的影响,并进行了实验验证。结果表明,当腔的菲涅耳数较大时,模式失配主要影响无源腔出射光功率的大小,而对其衰荡特征影响不大。在同等模式耦合条件下,选择功率大的光源及聚光面积大的探测器有利于提高测量精度。 相似文献
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研究了多注速调管TM410 模同轴输出腔中出现的外观品质因数高,模式频率间隔小以及工作模式场分布的均匀性差等问题,提出了一种设置短路杆和金属环的输出腔结构,从而改善了TM410 模输出腔上述三个方面的性能。通过分析发现,适当设置短路杆和重入环不仅可以使外观品质因数降低,还可以改善工作模式的场分布;设置重入环还可以增大工作模式和邻近模式的频率间隔。利用CST-MWS 软件,对X 波段具有短路杆和金属环的多注速调管TM410模同轴输出腔进行了模拟计算,其工作模式(TM410模)的外观品质因数降低了42.7%(从540.4 降至309.6),TM410 模与邻近模式的频率间隔均达到了1.3 GHz 以上,工作模式的场分布也变得均匀。 相似文献
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为了实现太阳光向激光的转化,设计并搭建了采用两级汇聚系统的实验系统。用菲涅耳透镜作为第1级汇聚系统,以漫反射锥型腔作为第2级汇聚系统,采用Nd:YAG作为工作物质。在太阳光的入射功率密度大约为950W/m2时,实验最高可得到13.3W的功率输出。用LASCAD软件对谐振腔进行模拟,得到了晶体棒工作时的温度分布和折射率分布;通过改变参量,对系统进行优化,得到了输出功率随腔长和输出镜反射率的变化规律,找到了最佳腔长为142mm,最佳输出镜反射率为91%。结果表明,通过调整腔长和输出镜反射率的大小,找到最佳值,可有效地提高太阳光直接抽运激光器的输出功率。 相似文献
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高次模多注速调管同轴输出腔性能改进的研究 总被引:1,自引:0,他引:1
该文针对工作在TM310模的多注速调管同轴输出腔中工作模式的场分布均匀性、外观品质因数及其与邻近模式的频率间隔等问题进行了研究,提出了一种带有短路杆和金属环的多注速调管同轴输出腔结构。分析发现,适当设置短路杆和金属环不仅可以使外观品质因数降低,还可以改善工作模式的场分布;而且设置金属环还可以增大TM310模和邻近模式的频率间隔以实现抑制杂模。利用仿真软件对X波段的同轴输出腔进行了模拟计算,计算结果与理论分析一致。在此基础上加工了冷测模型,测试结果表明TM310模与邻近模式的频率间隔均达到了1.2 GHz以上,外观品质因数从507.4降至193.5,工作模式的场分布也变得均匀。 相似文献
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The transverse mode structure of a tapered-wiggler free-electron laser (FEL) oscillator operating at full saturated intensity is analyzed numerically. The unique features of the FEL geometry, and particularly the refractive property of thee -beam, which acts like a series of small focusing lenses, tend to produce a steady-state mode structure different from the TEM00 mode of the cavity. The higher order mode content is especially evident in confocal cavities, since higher order modes constructively interfere on different round trips. Constructive addition of higher-order modes is also expected in practical FEL's operating at substantial power levels using near-concentric cavities. The presence of higher order modes has unusual effects on the intracavity intensity distribution of a confocal cavity, including different spot sizes on the front and rear mirrors and different transverse structure on forward and reverse passes. Nevertheless, the output beam quality is nearly diffraction limited for the low gain, low Fresnel number cases studied. Noticeable higher order mode content is also expected for near-concentric cavities. 相似文献
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本文给出了计算一般球面反射镜轴对称激光谐振腔场分布的方法.利用此方法,计算了小Fresnel数的光腔腔内的场分布及输出光束的强度分布.计算所得结果与实验观察到的现象相同. 相似文献
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N. L. Aleksandrov A. V. Chirkov G. G. Denisov D. V. Vinogradov W. Kasparek J. Pretterebner D. Wagner 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(9):1369-1385
The excitation of very high-order modes in circular waveguides has been performed in a cavity with a connected up-taper with a geometry similar to those used in gyrotrons. A Gaussian beam was coupled to the cavity which was made translucent by an array of holes. With the help of a special optics, the amplitude as well as the phase distribution of the beam was matched to the mode to be excited in the resonant cavity. By simple rotation of one mirror to adjust the phase distribution together with the change of frequency to match the resonance condition, a large number of modes could be produced with one experimental set-up. Field measurements in the output waveguide show a high mode purity of the radiation and confirm the calculations. The method can be used for cold tests of electrodynamic systems operating with these modes, e.g. quasi-optical converters for gyrotrons. 相似文献
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Because an active maser medium exhibits nonlinear gain saturation, the oscillating modes of an optical maser are expected to be somewhat different from those of the passive resonator. Statz and Tang [5] have obtained some numerical results for an active resonator with a pair of parallel-plane, infinite-strip mirrors. We have reformulated the problem for active resonators with circular mirrors of both parallel-plane and confocal geometries and have obtained numerical results using an iterative method of solution. We find the cardinal features of the active modes, such as mode patterns, diffraction losses, and resonant frequencies, to be essentially the same as those of the passive modes, even for unsaturated gains as high as three and a half dB per pass. The mode that predominates in an active Fabry-Perot resonator is found to be the lowest-order (TEM00 ) mode. However, the predominating modes in an active confocal resonator are found to depend on the Fresnel number; the larger the Fresnel number, the higher is the mode order. The study includes computations of field distributions, diffraction losses, and phase shifts of the steady-state predominating modes and of their output intensities as functions of unsaturated gain, saturation parameter, mirror transmissivity, scattering loss, and resonator geometry. 相似文献