Widely tunable SNAP microresonators via translation of side-coupled optical fibers

TL;DR

This paper presents a method to achieve widely tunable SNAP microresonators by translating side-coupled optical fibers, allowing precise control over their free spectral range for various optical applications.

Contribution

The study introduces a novel tuning technique for SNAP microresonators using fiber translation, enabling adjustable FSR with high precision and high Q-factors.

Findings

FSR tunable from 5 pm to 50 pm

Coupling length adjustable from 900 μm to 100 μm

Q-factor exceeds 10^5

Abstract

We demonstrate free spectral range (FSR) tunable Surface Nanoscale Axial Photonics (SNAP) microresonators induced by side-coupled parallel optical fiber segments. By translating one segment relative to the other, we tune the coupling length from $900~\mu$m to $100~\mu$m and thereby tune the microresonator FSR from $5$ pm to $50$ pm, with an estimated precision of better than $0.003$ pm. The microresonator Q-factor exceeds $10^5$ and can potentially be significantly increased in a clean lab environment. Possible applications of the demonstrated device include miniature and low-loss tunable delay lines and optical frequency comb generators, as well as ultraprecise tunable optical sensors.