Sparse Aperiodic Optical Phased Arrays on Polymer Integration Platform

We demonstrate solid-state optical beam-steering utilizing polymer waveguides as edge emitters to form optical phased arrays (OPAs) for operation at 1550 nm. Waveguide spacing below the wavelength is hindered in low index contrast OPAs by cross-coupling, leading to the formation of unwanted grating lobes in the far field. We employ non-uniform spacing between the 16 channels of the OPAs to suppress the grating lobes and improve the unambiguous beam steering range. Three different aperiodic layouts are fabricated and experimentally tested. Within a steering range of ±10° we achieve an average beamwidth of 0.45° with an ordered spacing layout, and 0.52° and 0.69° with a randomized spacing layout of
$8\lambda $
and
$5\lambda $
average spacing, respectively. With the latter we show suppression of the sidelobes of >11 dB and >6 dB within a steering range of ±5° and ±8°, accordingly. Power consumption of 1.28 mW/
$\pi $
per channel is achieved thanks to the excellent thermo-optic (TO) coefficient of the polymer platform. To the best of our knowledge, we are the first to demonstrate polymer-based OPAs with aperiodic spacing.