Observation of Aulter-Townes splitting in subwavelength grating metamaterial ring resonators

Subwavelength grating metamaterial (SGM) waveguide is typically treated as a homogeneous medium without considering intra-waveguide reflection. However, this approximation is not always valid, especially in resonators. In this paper, we show that the reflection-induced mutual coupling between the clock-wise and counter-clock-wise resonant modes in a subwavelength grating metamaterial waveguide ring resonator (SGMRR) breaks the degeneracy of the two modes, leading to the formation of Autler-Townes splitting. This phenomenon could be leveraged to improve the detection limit of SGMRR-based sensors.