Near-Zero Crosstalk and Ultra-Low Loss Waveguide Crossings Enabled by three-dimensional Ta2O5-on-LNOI Integrated Photonic Platform

TL;DR

This paper introduces a low-cost fabrication method for 3D waveguide crossings on a Ta2O5-on-LNOI platform, achieving near-zero crosstalk and ultra-low loss, advancing large-scale integrated photonics.

Contribution

It presents a novel fabrication technique exploiting edge rounding in CMP to create low-loss, low-crosstalk 3D waveguide crossings compatible with standard manufacturing.

Findings

Average loss below 0.002 dB

Crosstalk below -62 dB

Compatible with semiconductor technology

Abstract

Waveguide crossings represent one of the most critical components in very-large-scale photonic integration (VLSPI). Three-dimensional waveguide crossings, which distribute optical pathways across multiple planes, can achieve near-zero crosstalk and extremely low crossing-induced loss. However, they face an intrinsic trade-off between interlayer crossing performance and coupling efficiency. To address this challenge, we developed a low-cost fabrication method for 3D waveguide crossings by exploiting the edge rounding effect inherent to chemical mechanical polishing (CMP). Using this method, we demonstrate waveguide crossings with average loss below 0.002 dB and crosstalk below -62 dB on Ta2O5-on-LNOI integrated photonic platform. Our method maintains full compatibility with conventional semiconductor manufacturing technology and paves the way for realizing VLSPI on the thin-film lithium niobate platform.