Optically modulated waveguide-coupled spintronic terahertz radiation emitters

Increases in data bandwidth requirements are constantly pushing wireless communications networks to frequencies. With operating frequencies starting to approach the Terahertz (THz) band, it is important to develop compact, chip-based THz radiation sources that are compatible with both the semiconductor industry and the Si photonics scene. In recent years, spintronic THz emitters, thin film heterostructures with a stack thickness of 5 nm capable of producing THz pulses via femtosecond laser pulse excitation have been the subject of much interest due to their efficiency, small footprint, and ease of integration with various platforms. Here, we present spintronic THz radiation emitters on Si and SiO₂ substrates integrated with optical waveguides that allow for modulation of the generated THz radiation power by up to 87% via variation of the optical pump polarization. As a result of the gradual trend towards higher frequencies, we envision such structures as being utilised for various on-chip applications alongside electronic and photonic circuits.