Figure 3. Schematic of nanohole arrays and the experimental setup.

(a) SEM images of the nanohole arrays. The nanoholes array that can generate vortex beam with OAM is located at the center circle (region I), the outside ring (region II) is arranged to generate spherical beam. The insert show the arrangement of the elliptical nanoholes at different areas. (b) The schematic of the experimental setup for measuring the light intensity distribution that transmitted from the sample. The insert shows the interference results. Abbreviations for the optical components: QWP: quarter waveplate; LP: linear polarizer.