Fig. 1: Conceptual representation of frequency conversion in meta-molecules with a time-varying bond.
a Schematic of a meta-molecule composed of two coupled meta-atoms (metallic resonators). The time-varying bond strength of the molecule is denoted by J(t), while f0 represents the resonance frequency of the resonators. b Diagram illustrating the hybrid meta-molecule array and the experimental setup for THz pump-probe spectroscopy measurements. The arrival times of the pump and probe pulse peaks at the hybrid meta-molecule array are indicated as tJ and tp, respectively. The time delay is defined as tpp = tp - tJ. The input wave has a center frequency of f1, and the frequency of the output wave shifts to f0. c Absolute value of coupling coefficient |J| as a function of time. The top panel displays the bonding state of meta-molecules and energy level diagrams at different time intervals. τJ corresponds to the period required for breaking the meta-molecular bond. The calculated transmission spectra of the meta-molecules in the strong and weak bond regimes are presented on the left and right centers, respectively. f1 and f2 represent the two resonance frequencies of the meta-molecules in the strong bond regime. d Power spectra of the output waves at various tpp. The blue-shaded region and the red curve represent the power spectra of the input and output waves, respectively.
