Terahertz (THz) waves are located between microwaves and infrared light in the electromagnetic spectrum. They can pass through many materials without causing damage, making them useful for security scanning, medical imaging, and high-speed wireless communication. Unlike visible light or radio waves, THz waves can reveal structural details of biological molecules and penetrate nonmetallic objects like clothing and paper.

THz waves hold great promise, but to harness them effectively, their polarization (the direction in which the waves vibrate) must be controlled. Polarization control is crucial for optimizing THz applications, from enhancing data transmission to improving imaging and sensing.

Unfortunately, existing THz polarization control methods rely on bulky external components like wave plates or metamaterials. These solutions are often inefficient, limited to narrow frequency ranges, and unsuitable for compact devices. To overcome these limitations, researchers have been exploring approaches to control THz polarization directly at the source.