Speaker
Description
Spontaneous symmetry breaking (SSB) is a ubiquitous physical phenomenon in which a symmetric system abruptly evolves into an asymmetric state under infinitesimal perturbations. In nonlinear photonics, Kerr-mediated SSB has previously been demonstrated between counterpropagating modes in microresonators and between orthogonal polarization modes [1,2].
Here, we experimentally demonstrate color symmetry breaking in a silicon nitride microresonator driven bichromatically by two continuous-wave lasers addressing distinct resonator modes. Motivated by recent interest in dual-pump microresonator systems [3], we simultaneously sweep two pumps across neighbouring cavity resonances under nominally symmetric driving conditions. Above a threshold power, the system spontaneously develops an imbalance between the intracavity fields, causing one colour channel to dominate over the other despite the symmetry of the external excitation.
The observed asymmetry originates from cross-phase modulation, whereby small intensity fluctuations are amplified and drive the system away from its symmetric state. Experimental observations are supported by coupled-mode simulations and bifurcation analysis. In addition to saddle-node bifurcations associated with Kerr bistability, we identify pitchfork bifurcations marking the emergence of symmetry-broken states. Small differences in resonator quality factors introduce a controllable linear bias that determines the preferred symmetry-broken solution.
Unlike previously demonstrated forms of optical SSB, which are typically restricted to two-dimensional mode spaces, color symmetry breaking naturally extends to systems involving multiple frequency modes. This provides a new route towards high-dimensional nonlinear photonic dynamics and reconfigurable optical information processing. Furthermore, the dual-pump response can be continuously tuned to realise a wide range of nonlinear transfer characteristics, offering a promising platform for integrated all-optical activation functions in neuromorphic photonic hardware [4].
References:
[1] A. Ghosh et al., Laser Photon. Rev. 20, e01500 (2026).
[2] N. Moroney et al., Nat. Commun. 13, 398 (2022).
[3] N. B. Tomazio et al., ACS Photonics 12, 227–235 (2025).
[4] L. O. Trinchão et al., arXiv:2601.00792 (2026).
| I am the presenting author | Yes |
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