Selective linewidth control in a micro-resonator with a resonant interferometric coupler

TL;DR

This paper introduces a resonant interferometric coupler that enables continuous, selective control of the quality factor of specific resonances in a silicon nitride microresonator, enhancing application-specific spectral tuning.

Contribution

The work demonstrates a novel method for selectively tuning the Q-factor of individual microresonator resonances using a resonant interferometric coupler, with experimental validation.

Findings

Q-factor tunable from 65,000 to 3 million for targeted resonances

Untargeted resonances remain unaffected during tuning

Design scalable for multiple resonance control

Abstract

Optical microresonators are characterized by a comb of resonances that preserve similar characteristics over a broad spectral interval. However, for many applications it is beneficial to selectively control of the quality factor (Q) of one or only some resonances. In this work we propose and experimentally validate the use of a resonant interferometric coupler to selectively change the Q-factor of a target resonance in an integrated silicon nitride microresonator. We show that its Q-factor can be continuously tuned from 65000 to 3 milions, leaving the untargeted resonances uperturbed. Our design can be scaled to independently control several resonances.