3th International Congress of Engineering and Natural Sciences Studies, Ankara, Turkey, 24 - 25 May 2023, pp.109
Phase-modulated metasurfaces are meta-structures in which each metasurface unit cell is designed Phasemodulated metasurfaces are meta-structures in which each metasurface unit cell is designed according to a certain phase distribution to provide phase control of the electromagnetic wave. The desired phase response properties of the metasurface vary with the substrate and interface layer material type, size, shape, and rotational mode of the metasurface unit. Metalenses are metasurfaces where circular phase distributions are formed on the interface where light encounters. In this context, in this study, eight metalens unit cells that provide phase manipulation in the full phase range are designed to create the superficial phase layout required for the axicon focusing function. The designed unit cells are aperture-based nanoantennas opened in gold film coated on a silicon nitride membrane in nanometric thicknesses. Simulations are carried out at an operation wavelength of 850 nm. A circular arrangement of the designed cells at equal radial distances is created. In this way, circular phase rings that provide full phase transition on the metalens interface are formed. Under the limitations of the technical infrastructure of the analyses, with this proposed plasmonic metalens design, five focal points are identified. Focusing parameters such as focal length, numerical aperture, depth of focus, focus spot width, and focus efficiency are determined theoretically for each focal point.
Keywords: Axicon focusing, plasmonic metalens, focusing performance, circular phase distribution, nanoapertures.