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

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.