Observation of loss-enhanced magneto-optical effect

Magneto-optical (MO) effects have a pivotal role in modern photonic devices for light manipulation and sensing, but the study of these effects has so far been limited to the MO Faraday and Kerr effects. Conventional MO systems encounter considerable intrinsic losses, markedly hampering their ability to amplify the MO effects. Here we introduce a loss-enhanced MO effect to sublinearly amplify the frequency response of a non-Hermitian optical cavity under different background magnetic fields. This exceptional MO effect relies on an architecture of MO material embedded in a Fabry–Pérot cavity, accompanied by a polarization-dependent optical absorption, that is, linear dichroism, to construct a reconfigurable exceptional point. The experimental results show that two eigenmodes of the Fabry–Pérot cavity exhibit sublinear frequency splitting. By electrically reconfiguring the absorber, the eigenfrequency shift can be adaptively enhanced under different background magnetic fields. Using this effect, we demonstrate the detection of subtle magnetic field variations in a strong background, with the system’s response magnified by a factor exceeding 10 and sensitivity increased threefold compared with its conventional Hermitian counterpart. Our study leverages exceptional physics to study the MO effect and develops a new class of reconfigurable MO devices equipped with enhanced sensitivity for potential integration with photonic systems. The authors introduce a loss-enhanced magneto-optical effect and sublinearly amplify the frequency response of a non-Hermitian optical cavity under different background magnetic fields. This effect is exploited to detect subtle magnetic field variations against a strong background with enhanced system response and sensitivity.