Wireless communication between integrated optics nodes requires efficient photonic antennas to send and receive light. Radio-frequency engineering offers the idea of phased arrays
: arrays of many antenna units where each element is essentially an individually driven spherical wave source. Control of amplitude and phase of the feeding of each element allows it to synthesize complex beams. The authors realize an effective phased array in an integrated optics platform despite the fact that the technology forbids dense integration. In RF one packs antenna elements at subwavelength spacing, but in integrated optics each radiator requires its own feeding waveguide. As the waveguide network will occupy most of the wafer real estate, the question is which sparse geometrical arrangement of antenna elements still allows effective beam shaping. The authors take inspiration from aperiodicity in nature, realizing a CMOS-based sunflower seed arrangement of radiators. The distinct wave vector content of this arrangement makes it ideal for broadband directional antennas with superior side-lobe suppression, compared with grouping the same set of antenna elements in a periodic lattice. The notion that aperiodic and quasiperiodic geometries offer a bright future for beam shaping and diffraction is increasingly taking hold in optics, where the metasurfaces and plasmonics communities push phased arrays all the way to the nanoscale.
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