All-Optically Tunable Broadband Terahertz Modulators Based on Large-Area WSe₂/Si Heterojunction Grown by Sputtering...

Effective terahertz (THz) modulation remains a critical challenge for advancing THz technology. Recently, two-dimensional (2D) materials integrated with high-resistance silicon (Si) have emerged as promising heterojunction platforms for THz control. In this paper, we experimentally demonstrate an all-optically controlled THz modulator based on a large-area WSe₂/Si heterojunction, fabricated by magnetron sputtering of tungsten on Si followed by vacuum selenization. The device exhibits broadband modulation across 0.1-1.1 THz, achieving a modulation depth of 72% at a pump power of 1500 mW/cm², significantly higher than that of bare Si or pristine WSe₂ films. Moreover, we systematically analyze the underlying mechanism responsible for this enhanced performance. This study presents an effective and scalable strategy for THz modulation using 2D material/Si heterojunctions.