Opt Lett. 2018 Aug 15;43(16):4053-4056. doi: 10.1364/OL.43.004053.
Spherical microparticles have the ability for nonresonant focusing of light in the near field zone, forming nanojet (NJ) beams. Arbitrary-shaped microstructures, with wavelength-scale dimensions, may offer similar functionality with lower fabrication complexity. The focusing properties are ruled by the edge diffraction phenomenon. The diffraction of light on the edge of a dielectric microstructure forms a tilted focused beam whose deviation angle depends on the index ratio between the structure material and host medium. The beam geometry and field intensity enhancement can be tuned by varying the curvature of the edge line. Interference of edge diffracted waves from different segments of the edge line creates a condensed beam in the near field zone, the photonic nanojet.
球形微粒子具有在近场区域对光进行非共振聚焦的能力，形成纳米射流（NJ）光束。具有波长级尺寸的任意形状的微结构可能具有类似的功能，同时制造复杂性更低。聚焦特性受边缘衍射现象的控制。光在介电微结构边缘的衍射形成了倾斜聚焦光束，其偏转角取决于结构材料和主介质之间的折射率比。通过改变边缘线的曲率，可以调节光束几何形状和场强增强。来自边缘线不同部分的边缘衍射波的干涉在近场区域产生了一个凝聚光束，即光子纳米射流。
