# Controlling evanescent waves using silicon photonic all-dielectric metamaterials for dense integration

## TL;DR

This paper demonstrates that anisotropic all-dielectric metamaterials can significantly reduce evanescent wave decay, enabling ultra-compact, densely integrated silicon photonic circuits with minimal cross-talk and low propagation loss.

## Contribution

It introduces a novel approach using all-dielectric metamaterials to control evanescent waves, improving integration density without increasing propagation loss.

## Key findings

- Cross-talk reduced by over 30 times
- Bending loss reduced by over 3 times
- Propagation loss of 3.7 dB/cm achieved

## Abstract

Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves. We experimentally show the reduction of cross-talk by greater than 30 times and the bending loss by greater than 3 times in densely integrated, ultra-compact photonic circuit blocks. Our prototype all-dielectric metamaterial-waveguide achieves a low propagation loss of approximately 3.7 dB/cm, comparable to those of silicon strip waveguides. Our approach marks a departure from interference-based confinement as in photonic crystals or slot waveguides, which utilize nanoscale field enhancement. Its ability to suppress evanescent waves without substantially increasing the propagation loss shall pave the way for all-dielectric metamaterial-based dense integration.