Opt Lett. 2018 Jun 15;43(12):2840-2843. doi: 10.1364/OL.43.002840.
In this Letter, a singularity in the phase gradient is introduced as a new origin of the diffraction from phase objects. The continuity in the amplitude and phase of the wave and the singularity in the phase gradient are assumed to describe this phenomenon. Fresnel diffraction of Fresnel double mirror and biprism are studied as practical examples, and the diffracted intensity distribution is calculated. We show that the intensity of the diffracted field varies with an almost constant period along the average propagation direction. Using this value and the fringe spacing of the interference pattern on a plane normal to the average propagation direction, the angle between two interfering beams and the wavelength of the incident light could be simultaneously derived. The diffraction pattern of the Fresnel double mirror and Fresnel biprism were obtained experimentally, which were in good agreement with the theoretical results.
在这封信中，相位梯度中的奇点被引入作为相位物体衍射的新起源。假设波的幅度和相位连续，而相位梯度中的奇点来描述这一现象。我们研究了菲涅耳双镜和双棱镜的菲涅耳衍射作为实际例子，并计算了衍射强度分布。我们表明，沿平均传播方向，衍射场的强度以几乎恒定的周期变化。利用这个值和垂直于平均传播方向的平面上的干涉图案的条纹间距，可以同时推导出两个干涉光束之间的角度和入射光的波长。实验获得了菲涅耳双镜和菲涅耳双棱镜的衍射图案，它们与理论结果非常吻合。
