Exceptional coupling in extreme skin-depth waveguides for extremely low waveguide crosstalk

TL;DR

This paper demonstrates that exceptional coupling in extreme skin-depth waveguides can completely suppress waveguide crosstalk, enabling higher integration density in photonic chips with potential broad applications.

Contribution

It introduces the concept of exceptional coupling in eskid waveguides to achieve near-infinite coupling length and crosstalk suppression on a CMOS-compatible platform.

Findings

Waveguide crosstalk can be suppressed completely.

Exceptional coupling results in infinitely long coupling length.

Demonstration on silicon-on-insulator platform.

Abstract

Photonic chips can miniaturize complicate optical systems very tiny and portable, providing versatile functionalities for many optical applications. Increasing the photonic chip integration density is highly desired as it provides more functionalities, low cost, and lower power consumption. However, photonic chip integration density is limited by the waveguide crosstalk, which is caused by the evanescent waves in the cladding. Here we show that the waveguide crosstalk can be suppressed completely with the exceptional coupling in extreme skin-depth (eskid) waveguides. The anisotropic dielectric perturbations in the coupled eskid waveguides cause such an exceptional coupling, resulting in infinitely long coupling length. We demonstrate the extreme suppression of waveguide crosstalk via exceptional coupling on a silicon-on-insulator (SOI) platform, which is compatible with a complementary metal-oxide-semiconductor (CMOS) process. The idea of exceptional coupling in eskid waveguides can be applied to many other photonic devices as well, significantly reducing entire chip footprints.