Higher-order exceptional points (EPs) are non-Hermitian degeneracies at which three or more eigenvalues and eigenvectors simultaneously coalesce. EPs typically require fine-tuning of multiple parameters, whereas symmetry protection can reduce the dimensionality of the parameter space required for their realization. Here, we show that gauge flux provides a route to symmetry-controlled higher-order EPs. Using a three-level loop-interaction system formed by coupling a single-mode waveguide to an orbital-angular-momentum (OAM) waveguide, we demonstrate that a gauge flux can be introduced through mode rotation induced by a trench in the OAM waveguide. In the absence of gauge flux, the system lacks the symmetry required to support higher-order EPs. By contrast, a gauge flux of $\pi /2$ induces a non-Hermitian chiral symmetry, giving rise to a third-order EP. By tuning the coupling strength, we further realize switching between third- and second-order EPs. Our results establish gauge flux as an alternative degree of freedom for realizing and manipulating higher-order non-Hermitian degeneracies.

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• Photonics
• Synthetic gauge fields
• Exceptional points
• Waveguides