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

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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 1×7 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.
Funding Information
  • NSF (2034019-ECCS)
  • Air Force Research Laboratory (FA8750-20-P-1705)
  • STTR through Freedom Photonics

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