Design of Compact and Efficient Silicon Photonic Micro Antennas with Perfectly Vertical Emission

TL;DR

This paper presents a novel design methodology for silicon photonic micro-antennas that achieve high vertical emission efficiency, broad bandwidth, and low reflection, using advanced optimization and machine learning techniques.

Contribution

It introduces a combined adjoint optimization and machine learning approach to efficiently design high-performance, perfectly vertical silicon photonic antennas with broad bandwidth and low reflection.

Findings

Achieved 92% diffraction efficiency with a 3.6 μm antenna

Coupling efficiency over 81% with ultra-high NA fiber

Reflection below -20 dB over 200 nm bandwidth

Abstract

Compact and efficient optical antennas are fundamental components for many applications, including high-density fiber-chip coupling and optical phased arrays. Here we present the design of grating-based micro-antennas with perfectly vertical emission in the 300-nm silicon-on-insulator platform. We leverage a methodology combining adjoint optimization and machine learning dimensionality reduction to efficiently map the multiparameter design space of the antennas, analyse a large number of relevant performance metrics, carry out the required multi-objective optimization, and discover high performance designs. Using a one-step apodized grating we achieve a vertical upward diffraction efficiency of almost 92% with a 3.6 {\mu}m-long antenna. When coupled with an ultra-high numerical aperture fiber, the antenna exhibits a coupling efficiency of more than 81% (-0.9 dB) and a 1-dB bandwidth of almost 158 nm. The reflection generated by the perfectly vertical antenna is smaller than -20 dB on a 200-nm bandwidth centered at {\lambda} = 1550 nm.