Observation of higher-order exceptional points using frequency-dependent gain

Non-Hermitian systems exhibit exponentially amplified spectral sensitivity at higher-order exceptional points (HOEPs), where the eigenvalue response grows with the EP order. Conventional characterization relies on identifying reflection minima, implicitly imposing a fixed-gain constraint. Here, we demonstrate that the attainable order of the EP can be substantially elevated by replacing the fixed gain with a frequency-dependent gain, thereby obviating the necessity of nonlinear-gain mechanisms t