Waveguide-loaded silica fibers for coupling to high-index micro-resonators

TL;DR

This paper presents a novel method for efficiently coupling tapered silica fibers to high-index micro-resonators by loading the fibers with an adiabatic waveguide-coupler, significantly improving coupling efficiency and enabling advanced optical applications.

Contribution

Introduction of a waveguide-loaded fiber approach using angled-etching to enhance coupling to high-index micro-resonators, overcoming limitations of low refractive index fibers.

Findings

Enhanced coupling efficiency to silicon micro-resonators.

Observation of optical bistability at high powers.

Applicable to various resonator sizes and materials.

Abstract

Tapered silica fibers are often used to rapidly probe the optical properties of micro-resonators. However, their low refractive index precludes phase-matching when coupling to high-index micro-resonators, reducing efficiency. Here we demonstrate efficient optical coupling from tapered fibers to high-index micro-resonators by loading the fibers with an ancillary adiabatic waveguide-coupler fabricated via angled-etching. We demonstrate greatly enhanced coupling to a silicon multimode micro-resonator when compared to coupling via the bare fiber only. Signatures of resonator optical bistability are observed at high powers. This scheme can be applied to resonators of any size and material, increasing the functional scope of fiber coupling.