Polarization and wavelength agnostic nanophotonic beam splitter

TL;DR

This paper introduces a novel modal engineering approach in slotted waveguides to create ultra-wideband, polarization-insensitive optical beam splitters with relaxed fabrication tolerances for silicon photonics.

Contribution

The authors develop a new design strategy using modal engineering in slotted waveguides to achieve polarization-insensitive, broadband beam splitters with improved fabrication robustness.

Findings

Achieved polarization-independent transmission over 390 nm bandwidth.

Demonstrated tolerance to waveguide width deviations of ±25 nm.

Reported consistent -3±0.5 dB splitting performance across the bandwidth.

Abstract

High-performance optical beam splitters are of fundamental importance for the development of advanced silicon photonics integrated circuits. However, due to the high refractive index contrast of the silicon-on-insulator platform, state of the art Si splitters are hampered by trade-offs in bandwidth, polarization dependence and sensitivity to fabrication errors. Here, we present a new strategy that exploits modal engineering in slotted waveguides to overcome these limitations, enabling ultra-wideband polarization-insensitive optical power splitters, with relaxed fabrication tolerances. The proposed splitter relies on a single-mode slot waveguide which is transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate -3$\pm$0.5 dB polarization-independent transmission in an unprecedented 390 nm bandwidth (1260 - 1650 nm), even in the presence of waveguide width deviations as large as $\pm$25 nm.