Photonic molecules in the Terahertz - mode splitting in coupled dielectric whispering gallery mode resonators

We present an investigation of photonic molecules in the (sub-) terahertz range. We couple two dielectric whispering gallery mode resonators with matched resonance spectra over tens of resonances. The (loaded) quality (Q)-factors of the individual disks range from 50 - 800. We observe mode splitting for all modes in the range of 0.15 - 0.33 (0.29) THz for a set of polyethylene (quartz) disks with radius = 3 mm (1.8 mm). With increasing distance of the resonators, the splitting decreases due to reduced mode overlap, in very good agreement with numerical calculations. The frequency splitting of different modes is also in good agreement with the numerical calculation.