All-Optical Broadband Terahertz Modulator Based on CsPbX3(X = Cl, Br) Perovskite Quantum Dots Heterostructure

All-optical THz heterojunction modulators have gained significant attention to meet the demanding requirements of next-generation wireless communication technologies. Self-powered heterojunction photodetectors have high separation and utilization of photoinduced charge carriers even without external power sources. This high efficiency separation is attributed to the built-in electric field between heterojunction layers, a crucial factor for all-optical THz heterojunction modulators. However, CsPbX 3 /Si heterojunctions exhibit excellent optical and electrical properties, positioning them as promising candidates for high-performance all-optical terahertz (THz) modulators. Here, the perovskite quantum dots CsPbCl 3 /Si and CsPbBr 3 /Si are studied to achieve broadband modulation (0.3–1.6THz) at low laser power based on all-optically controlled terahertz modulators, with modulation depths of 81% and 70%, respectively, and the bare silicon exceeds this by 8 times. The results suggest that self-powered photodetectors could serve as a promising source for high-performance terahertz modulators. Additionally, THz-TDS emerges as a sensitive and noncontact technique for evaluating the performance of photodetectors.