Dual-tunable and high-efficiency multifunctional terahertz device based on black phosphorus and graphene metasurface

This paper proposes a dual-tunable and high-efficiency terahertz (THz) device based on black phosphorus (BP) and graphene metasurface with four functions, including broadband absorption, narrowband absorption, linear dichroism (LD) and electromagnetically induced transparency (EIT). Dynamic tunability is achieved by adjusting the carrier density of BP, the chemical potential of graphene and the conductivity of vanadium dioxide (VO2). When VO2 is in the metallic state, the device can work as a broadband absorber in the range of 1.18-3.49 THz with absorption rate above 90% and the relative bandwidth of 98.9%. The device also has a narrowband absorption function with an absorption rate of 99.9% at 4.19 THz. Additionally, the device can achieve LD function at frequencies of 4.6 THz and 3.81 THz, with peak LD values of 0.95 and -0.90, respectively. When VO2 is in the insulating state, the device shows an EIT function with a highly transparent window at 4.68 THz. It is worth noting that all functions are switchable and the operating frequencies are adjustable. The dual-tunable multifunctional device may have great potential in miniaturized THz systems.