EIT-Based Differential Sensors for Nondestructive Evaluation of Concrete Structures

We use dual-spiral transmission line stubs to generate the highly sensitive electromagnetically induced transparency (EIT) at radio frequencies. The phenomenon is the radio analog of the quantum interference that cancels photon absorption at a particular frequency, thereby creating a transparency window in an absorbing medium. The single-stub configuration produces a Lorentz resonance, which we exploit to characterize the dielectric constant of concrete samples. The dual-stub configuration introduces the interference at a nearby frequency (which can be tuned by stub length), creating a sharp EIT resonance. With the spiral stub shape, the resonance phenomenon can be observed at VHF frequencies, allowing deep energy penetration and also increasing the effective surface area for wave–matter interaction without increasing its physical cross-sectional area. We practically demonstrate nondestructive concrete analysis at 120-MHz frequency by characterizing pure, carbonized, and acidified concrete samples based on their dielectric constant. We apply EIT-based differential sensing, facilitating precise comparison between intact and affected concrete samples, which enables the detection of subtle variations associated with common concrete degradation factors.