Optically Modulated Waveguide-Coupled Spintronic Terahertz Radiation Emitters

Terahertz (THz) waves have garnered growing attention for applications in communication, imaging, and spectroscopy, yet compact and efficient on-chip THz sources remain scarce. In this work, we achieve the in-situ generation, modulation, and sensing of coherent THz radiation within a single chip-scale device. We fabricate a waveguide-fed spintronic THz emitter comprising a silicon dioxide layer sandwiched between two W/Fe/Pt multilayers, integrating THz emission and modulation functionalities into a monolithic platform. Magnetic-field and symmetry-dependent measurements under both normal and side illumination confirm that the emitted broadband THz radiation originates from spin-to-charge conversion in the W/Fe/Pt multilayer structure. We further demonstrate that, under side excitation, the amplitude of the THz signal can be efficiently controlled by varying the pump polarization, enabling all-optical in-situ modulation without any external components. Numerical simulations elucidate the physical mechanism underlying this polarization-dependent modulation. Finally, we employ the device to measure the characteristic spectral response of α-lactose, validating its potential for on-chip spectroscopic sensing. This work offers a compact and integrable strategy for the simultaneous generation and manipulation of THz waves, paving a promising route toward chip-scale THz communication, imaging, and sensing systems.