A spintronic THz emitter with a microscale stripe pattern enables the modulation of chirality during THz wave generation. Unlike traditional THz sources that rely on external optical components, this emitter incorporates polarization tuning directly into its design, streamlining the technology and enhancing its capabilities.
The emitter comprises thin-film layers of tungsten, cobalt-iron-boron, and platinum. When exposed to ultrafast laser pulses, the material generates a spin current, which is converted into an electrical charge through the inverse spin Hall effect. The emitter’s microscale stripe pattern alters charge distribution, forming a built-in electric field that influences the amplitude and phase of emitted THz waves. By designing different stripe arrangements, the researchers achieved precise polarization tuning without external optical components.
Simply rotating the emitter allows for flexible and efficient switching between linear, elliptical, and circular polarization states. Critically, the device maintains high-quality circular polarization with an ellipticity greater than 0.85 across a broad frequency range of 0.74–1.66 THz, demonstrating its efficiency in broadband polarization control.
This innovation promises to transform biomedical imaging, where it can enable earlier disease diagnosis through more accurate biomolecule detection. (Image credit: Q. Yang et al., 10.1117/1.AP.7.2.026007)
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