Abstract
This work presents a detailed modeling-based analysis of integrated micro-ring resonators used for absorption spectroscopy. Generally, sensors based on micro-ring resonators detect changes in the real part of the sensing medium refractive index, at critical coupling. In absorption spectroscopy, however, micro-ring resonators are used to measure changes in the imaginary part of the index and are most sensitive away from critical coupling, with separate maxima in the under- and over-coupled regimes. In this work, we present a detailed analysis of the under-coupled regime, explaining the relationships between sensitivity, mode confinement, and losses. The analysis is based on reverse-symmetry waveguides to increase the proportion of mode power in the sensing medium and incorporates a realistic model of propagation losses based on experimental measurements of sidewall roughness. The analysis demonstrates that the resonant nature of the sensor is most effective at small radii compared to a non-resonant structure of equal size and shows a behavior of diminishing returns at larger device sizes regarding sensitivity and elevated proportions of mode power in the evanescent field.
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription