High-efficiency one-dimensional metalens for 3D focusing

We demonstrate a high-efficiency on-chip one-dimensional metalens for three-dimensional (3D) light focusing. The metalens consists of a one-dimensional dielectric nano-antenna array, which scatters the evanescent wave of a nano-waveguide into free space and focuses this scattered light into a 3D ring. The corresponding phase profile of the metalens is controlled by the relative locations of antennas in the array. Through antenna-waveguide distance optimization, the designed metalens only scatters 1.5% of propagation light into free space and 55% of the scattered energy is focused into the 3D ring. When we use the antennas with an optimized shape, 50.18% of the focused energy is concentrated in a circular arc of the ring, which subtends an angle of 48°. This high-efficiency on-chip one-dimensional metalens is promising for non-invasive optical signal detection in photonic integrated chips.