Optically Pumped Ultrafast and Broadband Terahertz Modulation with Scalable Molecular Beam Epitaxy Grown MoTe ₂ /Si Heterostructures

Abstract Despite advancements in terahertz (THz) modulators, achieving a balance between large modulation depth (MD) and fast modulation speed in scalable devices remains a significant challenge. Optically pumped THz modulators with high MD, broad bandwidth, and fast response times are essential for progress in THz technology. Here, scalable MoTe ₂ /Si van der Waals (vdW) heterostructures are grown via molecular beam epitaxy (MBE) as an optically pumped THz modulators, leveraging its favorable band alignment and seamless integration with silicon complementary metal‐oxide semiconductor (CMOS) technology. High‐quality bilayer, 5‐layer, and 7‐layer MoTe ₂ films are grown on high‐resistivity silicon, with the bilayer modulator achieving a maximum 74.6% modulation depth under 355 nm illumination of 4.8 W mm ⁻² at 0.25 THz. The bilayer device exhibited fast rise and fall times of 1.8 and 0.6 µs, respectively, and provided broadband modulation across the 0.1 to 1.0 THz range. Furthermore, this work demonstrates that higher modulation depth significantly enhances THz imaging quality with promising applications in detecting pharmaceutical forgeries. Overall, these ultrafast, broadband THz modulators provide a promising route for advancing next‐generation THz technology, enhancing applications in wireless communication, precision detection, and high‐resolution THz imaging, fostering future innovation.