Large dynamic range terahertz phase shifter based on a graphene-metal hybrid metasurface

Dynamic phase modulators in terahertz (THz) are vital for broadband wireless communication, terahertz imaging, and radar technology. However, it is still difficult to realize a large phase shift in transmission mode and in broadband. In this work, we present a terahertz dynamic phase shifter based on a graphene-metal hybrid metasurface. The device can actively modulate the phase of terahertz waves by changing the Fermi level of the graphene patch inside the metal resonant cavity, and a maximum phase shift of 180° is achieved. Compared with the same type of devices that have been reported so far, the proposed approach overcomes the limitations of current single-layer transmission modes that have struggled to achieve dynamically tunable phase shifts exceeding 150°, while simultaneously enabling large phase shift modulation across broader frequency bands. Moreover, the frequency range with an adjustable phase exceeding 170° is as wide as 110 GHz. We investigate the physical mechanism of the dynamic phase shifter and establish the relationship between phase shift and the Fermi level of graphene. Our work provides deeper insights into terahertz dynamic phase shifters, which have potential applications in phased-array radar, broadband wireless communication, and other fields.