Wavelength-Independent Bragg-like Reflection in Uniaxial Bi-Anisotropic Media

We have recently shown that a uniform birefringent medium exhibits a circular Bragg phenomenon that relies solely on resonant tuning of the medium’s parameters, rather than on a particular wavelength resonance, thus rendering its electromagnetic response arbitrarily broadband. The resonant condition, however, necessitated a chirality parameter equal to the average refractive index. Here, we demonstrate that non-axial wave propagation in an axially bi-anisotropic uniaxial medium also enacts such a response and, moreover, relaxes the severity of the tuning condition, offering a convenient platform for controlling both the location of the resonance and the corresponding bandwidth. Anomalous wave propagation at a singular point is additionally identified, in the vicinity of which a remarkably high and intrinsically broadband refractive index can be realized. Recent demonstrations of meta-media with giant and controllable chirality pave the path towards the realistic embodiment of a highly efficient optical modulator.