Color symmetry breaking in a nonlinear optical microcavity

TL;DR

This paper reports the first observation of color symmetry breaking in a silicon nitride microcavity, revealing new nonlinear dynamics and enabling optical neural network functionalities.

Contribution

It demonstrates spontaneous color symmetry breaking at low power in a silicon nitride microcavity and introduces Kerr-based nonlinear activation functions for neuromorphic computing.

Findings

Color symmetry breaking occurs at as low as 19 mW.

The system produces sigmoid-, quadratic-, and leaky-ReLU-like responses.

Reveals new nonlinear dynamics in Kerr resonators.

Abstract

Spontaneous symmetry breaking leads to diverse phenomena across the natural sciences, from the Higgs mechanism in particle physics to superconductors and collective animal behavior. In photonic systems, the symmetry of light states can be broken when two optical fields interact through the Kerr nonlinearity, as shown in early demonstrations with counterpropagating and cross-polarized modes. Here, we report the first observation of color symmetry breaking in an integrated silicon nitride microring, where spontaneous power imbalance arises between optical mode at different wavelengths, mediated by the Kerr effect. The threshold power for this effect is as low as 19 mW. By examining the system's homogeneous states, we further demonstrate a Kerr-based nonlinear activation-function generator that produces sigmoid-, quadratic-, and leaky-ReLU-like responses. These findings reveal previously unexplored nonlinear dynamics in dual-pumped Kerr resonators and establish new pathways towards compact, all-optical neuromorphic circuits.