Kerr-Nonlinearity-Induced Mode-Splitting in Optical Microresonators

TL;DR

This paper experimentally demonstrates Kerr nonlinearity-induced resonance splitting in optical microresonators, enabling simultaneous multi-wavelength resonance and potential applications in photonic devices such as filters and memories.

Contribution

The study reveals how Kerr nonlinearity causes resonance splitting in microresonators and introduces a pump-probe spectroscopy method to measure this effect at low power levels.

Findings

Resonance splitting up to 35 cavity linewidths at 10 mW pump power.

Resonance splitting can be achieved with as little as 286 μW power.

Threefold resonance splitting observed with four-wave mixing and counterpropagating lasers.

Abstract

The Kerr effect in optical microresonators plays an important role for integrated photonic devices and enables third harmonic generation, four-wave mixing, and the generation of microresonator-based frequency combs. Here we experimentally demonstrate that the Kerr nonlinearity can split ultra-high-Q microresonator resonances for two continuous-wave lasers. The resonance splitting is induced by self- and cross-phase modulation and counter-intuitively enables two lasers at different wavelengths to be simultaneously resonant in the same microresonator mode. We develop a pump-probe spectroscopy scheme that allows us to measure power dependent resonance splittings of up to 35 cavity linewidths (corresponding to 52 MHz) at 10 mW of pump power. The required power to split the resonance by one cavity linewidth is only 286${\mu}$W. In addition, we demonstrate threefold resonance splitting when taking into account four-wave mixing and two counterpropagating probe lasers. These Kerr splittings are of interest for applications that require two resonances at optically controlled offsets, eg. for opto-mechanical coupling to phonon modes, optical memories, and precisely adjustable spectral filters.