Patterned GaN/graphene Schottky heterojunction-metasurface hybrid for ultrasensitive terahertz modulation under dual stimuli

Patterned GaN/graphene Schottky heterojunctions have remarkable optoelectronic properties, enabling effectively namic modulation of light-matter interactions. Combining them with metasurfaces is of great potential to develop optical devices. In this paper, a device based on a patterned GaN/graphene heterojunction integrated with a metasurface is proposed. It operates under the excitation of pump light or bias voltage (V_b), with the Fermi level (<i>E_F</i>) of graphene shifting between the valence band, Dirac point, and conduction band as the laser power density (LPD) or V_b increases. This leads to a significant modulation of the amplitude and phase of the terahertz (THz) transmission, which shows a tendency to first enhance and then weaken, and exhibits unique modulation properties near the Dirac point. Experimental results demonstrate that the device achieves a maximum modulation depth of 93% at the V_b of 4 V. Additionally, the maximum phase modulation reaches 40° at the LPD of 33.1 mJ/cm². The device performs as multidimensional dynamic modulation of THz waves. This work provides new insights into the development and application of high efficiency THz modulators.