Reversed Cherenkov radiation via Fizeau–Fresnel drag

It has long been thought that the reversed Cherenkov radiation is impossible in homogeneous media with a positive refractive index n. Here, we break this long-held belief by revealing the possibility of creating reversed Cherenkov radiation from homogeneous positive-index moving media. The underlying mechanism is essentially related to the Fizeau–Fresnel drag effect, which provides a unique route to drag the emitted light in the direction of the moving medium and thus enables the possibility of dragging the emitted light in the opposite direction of the moving charged particle. Moreover, we discover the existence of a threshold for the velocity vmedium of moving media, only above which, namely, vmedium>c/n2, the reversed Cherenkov radiation may emerge, where c is the velocity of light in vacuum. Particularly, we find that the reversed Cherenkov radiation inside superluminal moving media (i.e., vmedium>c/n) can become thresholdless for the velocity of moving charged particles.