On-Chip Interferometric Excitation of an Infinity-Loop Microresonator

TL;DR

This paper demonstrates a fully integrated, phase-stable interferometric excitation method for an infinity-loop microresonator, enabling precise control of intracavity energy distribution and power enhancement through phase manipulation.

Contribution

It introduces an integrated interferometric excitation scheme and extends coupled-mode theory to include interference effects, advancing control of resonator modes.

Findings

Phase control governs intracavity energy distribution.

Up to twofold increase in circulating power compared to single-port excitation.

Platform enables reproducible phase-dependent studies in non-Hermitian photonics.

Abstract

Integrated photonics is a powerful platform for exploring Hermitian and non-Hermitian physics. Beyond device geometry, controlling how resonators are driven is crucial to access and tailor their modes. Coherent excitation via multiple input ports (interferometric excitation) enables such control, but its accurate description requires extending standard temporal coupled-mode theory to include interference between excitation pathways. Experimental realizations have so far been limited by phase-unstable, off-chip interferometers. Here we implement a fully integrated, phase-stable interferometric excitation scheme for an infinity-loop-microresonator, an established structure operating on an exceptional surface, and use it to test the extended theory. Phase-resolved measurements in the linear and thermo-optic nonlinear regimes show that the relative phase between inputs governs the intracavity energy distribution, enabling up to a twofold increase of the circulating power compared to single-port excitation. This integrated platform enables reproducible studies of phase-dependent effects and coherent-control schemes in non-Hermitian photonic devices.