An electrically driven terahertz metamaterial PIN modulator

A terahertz (THz) amplitude modulator based on a silicon p–i–n structure integrated with a planar metamaterial grating is experimentally demonstrated for free-space operation. Electrical modulation is achieved via bulk injection of nonequilibrium carriers into high-resistivity silicon, resulting in enhanced absorption of terahertz radiation in resonant modes of the structure. Owing to strong electromagnetic field confinement, a modulation depth of up to 26.7 dB is achieved. Time-resolved measurements reveal a switching time of 5.8 μs, governed by carrier recombination dynamics in the silicon bulk. The demonstrated modulator provides an efficient and CMOS-compatible solution for terahertz communication and imaging systems.