We propose a novel experimental method for probing light dark matter candidates. We show that an electro-optical material’s refractive index is modified in the presence of a coherently oscillating dark matter background. A high-precision resonant Michelson interferometer can be used to read out this signal. The proposed detection scheme allows for the exploration of an uncharted parameter space of dark matter candidates over a wide range of masses—including masses exceeding a few tens of microelectronvolts, which is a challenging parameter space for microwave cavity haloscopes.

• Received 3 July 2023
• Revised 8 November 2023
• Accepted 5 February 2024

DOI:https://doi.org/10.1103/PhysRevLett.132.101001

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Published by the American Physical Society