Low-loss mode converter for coupling light into slotted photonic crystal waveguide

TL;DR

This paper presents a highly efficient, low-loss adiabatic mode converter for silicon slot waveguides, significantly improving coupling efficiency into slotted photonic crystal waveguides with a novel design and experimental validation.

Contribution

The paper introduces a new adiabatic mode converter with ultra-low insertion loss and enhanced coupling efficiency for large-slot photonic crystal waveguides, outperforming conventional V-shape converters.

Findings

Insertion loss as low as 0.08dB achieved

0.1dB lower loss than V-shape converter

Coupling efficiency improved by up to 3.5dB

Abstract

We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08dB. Our mode converter provides 0.1dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5dB compared to the V-shape mode converter, over the slow-light wavelength region.