# Extracting losses from asymmetric resonances in micro-ring resonators

## TL;DR

This paper develops a new model that accounts for reflections causing asymmetry in micro-ring resonator resonances, enabling more accurate extraction of propagation losses from their transmission spectra.

## Contribution

A novel model incorporating reflections to accurately describe asymmetric resonances in micro-ring resonators, improving loss measurement reliability.

## Key findings

- The model accurately fits asymmetric resonances caused by reflections.
- Full-wave simulations validate the model's effectiveness.
- Propagation loss coefficients are determined more reliably with the new model.

## Abstract

Propagation losses in micro-ring resonator waveguides can be determined from the shape of individual resonances in their transmission spectrum. The losses are typically extracted by fitting these resonances to an idealized model that is derived using scattering theory. Reflections caused by waveguide boundaries or stitching errors, however, cause the resonances to become asymmetric, resulting in poor fits and unreliable propagation loss coefficients. We derive a model that takes reflections into account and, by performing full-wave simulations, we show that this model accurately describes the asymmetric resonances that result from purely linear effects, yielding accurate propagation loss coefficients.