Picosecond mode switching and Higgs amplitude mode in superconductor-metal hybrid terahertz metasurface.

The ultrafast modulation of terahertz (THz) waves is essential for numerous applications, such as high-rate wireless communication, nonreciprocal transmission, and linear frequency conversion. However, high-speed THz devices are rare due to the lack of materials that rapidly respond to external stimuli. Here, we demonstrate a dynamic THz metasurface by introducing an ultrathin superconducting microbridge into metallic resonators to form a superconductor-metal hybrid structure. Exploiting the susceptibility of superconducting films to external optical and THz pumps, we realized resonance mode switching within a few picoseconds. The maximum on/off ratio achieved is 11 dB. The observed periodic oscillation of transmission spectra both in the time and frequency domain under intense THz pump pulse excitation reveals the excitation of Higgs amplitude mode, which is used to realize picosecond scale THz modulation. This study opens the door to ultrafast manipulation of THz waves using collective modes of condensates, and highlights an avenue for developing agile THz modulation devices.