Speaker
Description
Through left- or right-handed twisting, we investigate the impact of mirror-asymmetry (chirality) of the conducting boundary conditions of an equilaterial triangular cross section electromagnetic resonator. We observe the generation of eigenmodes with nonzero electromagnetic helicity as a result of the coupling of near degenerate $\mathrm{TE}_{11(p+1)}$ and $\mathrm{TM}_{11 p}$ modes. This can be interpreted as an emergence of magnetoelectric coupling, which in turn produces a measurable shift in resonant mode frequency as a function of twist angle. We show that this coupling mechanism is equivalent to introducing a nonzero chirality material parameter $\kappa_{\text {eff }}$ or axion field $\theta_{\text {eff }}$ to the medium. Our findings demonstrate the potential for real-time, macroscopic manipulation of electromagnetic helicity.
