High speed electrically-controlled terahertz modulator

•The terahertz modulator is made on GaAs-based high electron mobility transistors.•The dynamical response to incident terahertz waves was investigated.•An ultrafast modulation speed over 11MHz can be achieved. We have developed an electrically-controlled terahertz modulator which can be used to realize amplitude modulation of terahertz waves at an extremely high speed. The terahertz modulator is made on GaAs-based high electron mobility transistors (HEMTs) array on which numerous split-ring resonators (SRRs) are formed. The device exhibits the capability of dynamical response to incident terahertz waves under a fast time-varying voltage. Our measurement results reveal that an ultrafast modulation speed over 11MHz under an applied AC gate voltage can be achieved. With the resistance and the capacitance of HEMTs further optimized, it was demonstrated that the HEMT/SRR-based modulator may operate at an even higher modulation frequency.