Fig. 1. (a) Schematic of multi-focus optical fiber metalens. (b) Schematic of a unit cell composed of a single RDR. The light is incident from the fiber, and the polarization is along the y direction. (c) The phase (black line) and transmittance (red line) variations of the transmitted light with the width W of single RDR.

Fig. 2. (a) Phase distributions of the fiber lens. Solid line: analytical phase of the lens with its focal length of 100 µm. Blue points: digitized phase profile based on FDTD simulation. (b) Calculated intensity distribution of the fiber lens with the focal length of 100 µm in the x–z plane. (c) The intensity profile across the focal plane (z=100µm) of the fiber lens.

Fig. 3. Discretized phase distributions based on (a) interleaving meta-atoms and (b) lens aperture division methods for the focal lengths of 50 and 100 µm. Solid lines: analytical phases. Blue points: the positions and discretized phases of RDRs used in the calculation.

Fig. 4. Intensity distributions of bifocal fiber lenses designed by (a)–(c) interleaving meta-atoms and (d)–(f) lens aperture division. The intensity distributions (a), (d) in the x–z plane, (b), (e) along the z axis, and (c), (f) at the focal plane (z=50 and 100 µm).

Fig. 5. Intensity distributions of bifocal fiber lens based on interleaving meta-atoms for different incident wavelengths. The intensity distributions (a) in the x–z plane and (b) along the z axis.

Fig. 6. Intensity distribution of three-focus fiber lens.