THz modulators based on the active GaN-HEMT metasurface

In this paper, we present a series of composite metamaterial THz modulators that combine optimized metallic metasurface with AlGaN/GaN heterostructure array to realize the amplitude and phase modulation of terahertz waves. Embedded with the nanostructured 2DEG layer of GaN HEMT, the resonance intensity and surface current circuit of the resonant modes in the metamaterial unit can be dynamically manipulated by electrical control of the carrier distribution and depletion of the 3 nm-2DEG. In real-time dynamic tests, THz spatial amplitude modulator achieves 93% modulation depth and 3 GHz modulation speed. THz spatial phase modulator achieves a 137 degree phase shift with an external controlling voltage of only several volts in the THz transmission mode.