摘要:
实验研究及理论分析了光波场中边位错向螺旋位错的转化行为.设计了围绕中心沿角向周期排列的多边位错相位结构,实验上通过计算全息图法研究了其对高斯光束的调制作用以及调制光束的传播特性.结果表明,随着调制光束逐渐演化为类涡旋光束,多边位错结构可以转化为螺旋位错,且位错结构的总相位变化守恒.结合光场的线动量密度图详细分析了该演化过程,并进一步讨论了多边位错结构中的相位突变值对螺旋位错转化的影响,给出了决定螺旋位错拓扑荷值的定量关系式.
关键词:
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边位错
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螺旋位错
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涡旋光束
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拓扑荷
Abstract:
Transformation of edge-dislocations to screw-dislocations in the optical field is experimentally and numerically demonstrated. A special multi-edge-dislocation structure is designed by arranging multiple edge-dislocations, which have the same phase-step value, periodically along the azimuthal orientation. Experimentally, in virtue of the computer-generated holography, a Gaussian beam is modulated by the multi-edge-dislocation, whose propagation dynamics is investigated as well. The results reveal that the multi-edge-dislocation can be converted into a screw-dislocation with the evolution of the Gaussian beam into a vortex-like beam. What is more, the sum phase change of the dislocations is conserved in this process. Then, the experimental results are verified by numerical simulations, and discussed in detail by analyzing the evolutions of the linear momentum density. Furthermore, the influence of the phase-step value of the edge-dislocation on the transformation is discussed, which illustrates the quantitative relation between the phase-step value and the topological charge of crew-dislocation.
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