利用干涉光场的相位涡旋测量拉盖尔-高斯光束的轨道角动量

对拉盖尔-高斯光束经多圆孔衍射屏在远场平面上形成的干涉光场的相位和零值线进行了计算模拟.当入射光束的轨道角动量量子数为零时,实部零值线与虚部零值线在干涉光场中心点不相交,因而在该点上不能形成相位涡旋.当入射光束的轨道角动量量子数为+1和-1时,实部零值线与虚部零值线在干涉光场中心垂直并相交,干涉光场相应位置处的相位涡旋的符号相反.当入射光束的轨道角动量量子数为±2和±3时,有四条零值线相交于干涉光场的中心点上,并且实部零值线和虚部零值线交替分布,该交点处形成的相位涡旋的拓扑荷的值恰好与拉盖尔-高斯光束的轨道角动量量子数相等.这种结果可以用来测量涡旋光束的轨道角动量.

Measurement of orbital angular momentum of Laguerre-Gaussian beam by using phase vortices of interference fields

The phase and the zero-contour of the real part and the imaginary part of the interference field on a far-field plane generated by multi-aperture diffraction screen are simulated. It is found that when the orbital angular momentum quantum number of incident beam is equal to zero, at the center of interference field the zero-lines cannot cross each other, therefore, thereby the phase vortices cannot form. When the orbital angular momentum quantum numbers of incident beam are opposite to each other in sign, namely -1 and +1 at the center of interference field the zero-lines are perpendicular to and cross each other, the signs of the phase vortices at the corresponding positions in interference fields are also opposite to each other. When the orbital angular momentum quantum numbers of incident beam are equal to ±2 and ±3, there are four zero-lines that cross each other at the center of interference fields, where the topological charge values of phase vortices are just equal to the orbital angular momentum quantum numbers of the Laguerre-Gaussian beam. Therefore, these results can be used to measure the orbital angular momentum of optical vortex beam.