Fine-Resolution Silicon Photonic Wavelength-Selective Switch Using Hybrid Multimode Racetrack Resonators

TL;DR

This paper presents a silicon photonic wavelength-selective switch with high resolution and low crosstalk, achieved through hybrid multimode racetrack resonators, enabling scalable multi-channel optical communication systems.

Contribution

The work introduces a novel design and synthesis procedure for high-Q racetrack resonators and demonstrates a scalable, multi-channel WSS with fine resolution and low crosstalk on silicon photonics.

Findings

Achieved ~1 dB drop-port loss and 2 GHz linewidth in racetrack filters.

Demonstrated three-channel operation with 10 GHz spacing and low crosstalk (<-25 dB).

Validated demultiplexing on 8 GHz and 10 GHz grids using the WSS.

Abstract

In this work, we describe a procedure for synthesizing racetrack resonators with large quality factors and apply it to realize a multi-channel wavelength-selective switch (WSS) on a silicon photonic chip. We first determine the contribution of each component primitive to propagation loss in a racetrack resonator and use this data to develop a model for the frequency response of arbitrary order, coupled-racetrack channel dropping filters. We design second-order racetrack filters based on this model and cascade multiple such filters to form a 1x7 WSS. We find good agreement between our model and device performance with second-order racetrack that have ~1 dB of drop-port loss, ~2 GHz FWHM linewidth, and low optical crosstalk due to the quick filter roll-off of ~ 5.3 dB/GHz. Using a control algorithm, we show three-channel operation of our WSS with a channel spacing of only 10 GHz. Owing to the high quality factor and quick roll-off of our filter design, adjacent channel crosstalk is measured to be <-25 dB for channels spaced on a 10 GHz grid. As a further demonstration, we use five of seven WSS channels to perform a demultiplexing operation on both an 8 GHz and a 10 GHz grid. These results suggest that a low-loss WSS with fine channel resolution can be realized in a scalable manner using the silicon photonics platform.