Fig. 1. THz transmission spectra based on 180 nm thick YBCO superconducting metamaterial[21]

Fig. 2. Metamaterial based on superconducting NbN film. (a) SEM image; (b) unloaded quality factor (Q) versus temperature[23]

Fig. 3. Electrical modulator based on superconducting Nb film. (a) Sub-THz radiation modulated by passing current; (b) micrograph of sample with horizontal arrows indicating the direction of electric current; (c) detailed dimensional drawing of structural unit of sample; (d) THz transmission spectra for temperatures below and above superconducting transition temperature (9 K)[25]

Fig. 4. THz superconducting electrical modulator. (a) Geometric dimension of metamaterial elementary unit; (b) schematic ofmodulator; (c) THz signals with different modulation frequencies in dynamic system measurement[27]

Fig. 5. Fitting parameters extracted from experimentally measured transmission spectrum using hybrid model[37]