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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.01469 |
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Table of Contents:
- Nonlinear energy exchange between vibrational modes underlies phenomena ranging from internal resonance to wave mixing, yet modal interactions are typically inferred from frequency-domain signatures rather than directly observed in space. Here, we present real-space imaging of nonlinear modal energy routing in a near-mirror-symmetric microelectromechanical resonator using phase-locked multi-harmonic stroboscopic interferometry. By reconstructing the spatial eigenmode content of individual harmonic components, we directly resolve the energy transfer pathway between interacting modes. Our measurements reveal that nonlinear energy exchange is not governed by frequency proximity alone. Even when harmonic frequencies lie closer to an opposite-symmetry mode, energy transfer remains strongly suppressed unless the interacting modes share identical spatial symmetry. A reduced two-mode model incorporating geometric nonlinearity shows that the intermodal coupling terms factorize into a single symmetry-determined modal-overlap integral, establishing spatial parity as the fundamental admissibility condition for nonlinear coherent energy exchange. These results demonstrate that symmetry, rather than spectral detuning alone, governs nonlinear modal coupling and introduce real-space nonlinear modal imaging as a general framework for controlling energy flow in nonlinear wave systems.