Highly efficient ultra-broad beam silicon nanophotonic antenna based on near-field phase engineering

TL;DR

This paper introduces a novel nanophotonic antenna design that uses near-field phase engineering to achieve high efficiency, ultra-broad beamwidth, and compact size, advancing optical phased array technology.

Contribution

The paper presents a new near-field phase-engineering approach for nanophotonic antennas, enabling ultra-broad beams with high efficiency and compact footprint on a silicon platform.

Findings

Radiation efficiency of 82% achieved

Ultra-broad beam width of 52° and 62°

Compact footprint of 3.1 μm × 1.75 μm

Abstract

Optical antennas are a fundamental element in optical phased arrays (OPA) and free-space optical interconnects. An outstanding challenge in optical antenna design lies in achieving high radiation efficiency, ultra-compact footprint and broad radiation angle simultaneously, as required for dense 2D OPAs with a broad steering range. Here we demonstrate a fundamentally new concept of a nanophotonic antenna based on near-field phase-engineering. By introducing a specific near-field phase factor in the Fraunhofer transformation, the far-field beam is widened beyond the diffraction limit for a given aperture size. We use transversally interleaved subwavelength grating nanostructures to control the near-field phase. The antenna reaches a radiation efficiency of 82%, a compact footprint of 3.1 um * 1.75 um and an ultra-broad far-field beam width of 52{\deg} and 62{\deg} in the longitudinal and transversal direction, respectively. This unprecedented design performance is achieved with a single-etch grating nanostructure in a 300-nm SOI platform.