High-resolution broadband characterization of resonance dispersion in an optical microresonator

TL;DR

This paper introduces a precise, fibered method for measuring the free spectral range of silicon nitride microresonators over a 5 THz bandwidth, enabling detailed dispersion analysis crucial for Kerr frequency combs.

Contribution

A simple, highly accurate technique using a high-resolution wavemeter for broadband dispersion measurement in integrated microresonators.

Findings

Measured second- and third-order free spectral range expansion coefficients.

Achieved 0.4 MHz resolution over 5 THz bandwidth.

Enabled robust dispersion characterization for photonic applications.

Abstract

Accurate knowledge of the uneven free spectral range of an optical microresonator, which provides direct insight into group velocity dispersion, is essential for understanding and controlling Kerr frequency comb dynamics. In this work, we present a simple and highly precise method formeasuring the free spectral range over a 5 THz bandwidth in silicon nitride microresonators, leveraging a wavemeter with 0.4 MHz resolution. Our fully fibered plug-and-play experimental setup enables the accurate extraction of resonance frequencies. By carefully analyzing the spectral position of each resonance, we measure both second- and third-order free spectral range expansion coefficients. This approach offers a robust and accessible tool for dispersion characterization in integrated photonic circuits, paving the way for next-generation of Kerr comb sources and quantum photonic technologies.