High-Power-Handling GaN Terahertz High-Speed On-Chip Modulator Based on Fin-Line Double-Layer Near-Field Coupling

To address the technical challenges in the coordinated optimization of power handling, modulation rate, and system integration for traditional terahertz modulators, this paper presents a high-power-handling gallium nitride (GaN) terahertz high-speed on-chip modulator operating in the 140 GHz frequency band. The device employs a fin-line double-layer near-field coupling structure and incorporates a resonant unit cell design loaded with GaN Schottky barrier diodes (SBDs). By controlling the switching states of the diodes, dynamic switching between dual-gap resonance mode and closed-ring resonance mode is achieved, realizing a modulation depth of 20 dB and a low insertion loss of 6 dB within the 139.4-149 GHz frequency range. Furthermore, the electric field peak intensity is effectively reduced through the expansion of metal areas on both sides of the resonant unit cell gap. Combined with the high breakdown field strength (3.3 MV/cm) of GaN material, a power capacity breakthrough of 175 mW is achieved. The zero/reverse bias strategy on diodes during the modulator’s off-state suppresses thermal accumulation in conducting diodes, ensuring stable high-power operation. Experimental results demonstrate that the modulator supports 25 Gbps high-speed data transmission, providing an on-chip solution with both high power handling and high transmission rate for terahertz communication systems.