Automatic Resonance Alignment of High-Order Microring Filters

TL;DR

This paper presents an automatic feedback-based method for tuning high-order microring filters to achieve precise resonance alignment, significantly reducing passband ripples and centering the passband at a reference wavelength.

Contribution

It introduces a novel automatic resonance tuning technique for high-order microring filters using a simple feedback system and demonstrates its effectiveness on fabricated silicon photonics devices.

Findings

Effective resonance alignment reduces passband ripples.

Method works across multiple dies and arbitrary wavelengths.

Demonstrates repeatability and robustness of tuning process.

Abstract

Automatic resonance alignment tuning is performed in high-order series coupled microring filters using a feedback system. By inputting only a reference wavelength, a filter is tuned such that passband ripples are dramatically reduced compared to the initial detuned state and the passband becomes centered at the reference. The method is tested on 5th order microring filters fabricated in a standard silicon photonics foundry process. Repeatable tuning is demonstrated for filters on multiple dies from the wafer and for arbitrary reference wavelengths within the free spectral range of the microrings.