Opt Lett. 2018 Dec 15;43(24):5969-5972. doi: 10.1364/OL.43.005969.
We demonstrate both experimentally and numerically a new type of hole array structure that exhibits optically diffractive focusing phenomenon. The hole arrays are designed based on the aperiodic Vogel spirals. In contrast to periodic and quasi-periodic hole arrays that contain discrete Bragg peaks in reciprocal space, the Vogel spiral hole arrays have particularly continuous Fourier components with circular symmetry, which enables optical wave focusing into a diffraction-limited hotspot for a wide range of incident wavelengths. We further demonstrate that the diffracted fields contain local orbital angular momentum (OAM) leading to rotations of the diffractive circular rings around the center, although the total OAM is zero.
我们通过实验和数值模拟展示了一种新型的孔阵列结构，该结构表现出光学衍射聚焦现象。孔阵列是基于非周期性 Vogel 螺旋设计的。与在倒易空间中包含离散布拉格峰的周期性和准周期性孔阵列不同，Vogel 螺旋孔阵列具有特别连续的具有圆对称性的傅里叶分量，这使得光能够聚焦到一个宽波长范围内的衍射极限热点。我们进一步证明，尽管总轨道角动量为零，但衍射场包含局域轨道角动量（OAM），导致衍射圆环围绕中心旋转。
