Double Resonance Strategy for Interferometric Detection of Axions

Abstract

We propose a double-resonant interferometric strategy for axion dark matter detection that combines microwave circuit resonance with Fabry--P\'erot optical enhancement. In a strong magnetic field, axion--photon mixing induces a weak oscillating electric field, which is first amplified by a resonant circuit and then transduced into an optical phase shift via the electro-optic effect. Multiple coherent optical passes through the electro-optic medium accumulate this phase shift, enabling interferometric readout using mature optical techniques. We present the basic operating principle, discuss material requirements, and estimate the achievable sensitivity. For representative parameters, the projected reach extends into the parameter space of well-motivated QCD axion models.