# An all-dielectric bowtie waveguide with deep subwavelength mode confinement

## TL;DR

This paper introduces an all-dielectric bowtie waveguide that achieves deep subwavelength mode confinement and lossless propagation, advancing nanoscale photonic integration without metal-related losses.

## Contribution

It presents a novel all-dielectric bowtie waveguide design with subwavelength confinement and lossless quasi-TM mode, surpassing plasmonic waveguides in propagation length.

## Key findings

- Supports a lossless quasi-TM eigenmode
- Achieves smaller mode area than hybrid plasmonic waveguides
- Compatible with semiconductor fabrication techniques

## Abstract

To fulfil both size and power requirements for future photonic integrated circuits, an effective approach is to miniaturize photonic components. Surface plasmon polariton (SPP) is one of the most promising candidates for subwavelength mode confinement, however, structures based on SPP are subject to inevitable high propagation loss. Here, we report an all-dielectric bowtie (ADB) waveguide consisting of two identical silicon wedges embedded in a silica cladding with a nanoscale gap. Because of successive slot and antislot effects, the gap behaves as a 'capacitor-like' energy storage that makes the ADB waveguide have similar or even smaller mode area than the hybrid plasmonic waveguides recently reported. What is more important is that the ADB waveguide supports a quasi-TM eigenmode, which is lossless fundamentally because of no metal constituent. This makes our ADB waveguide have essential development in propagation length compared with the plasmonic waveguide. The ADB waveguide is fully compatible with semiconductor fabrication techniques and could give rise to truly nanoscale semiconductor-based photonics.