Phys.org July 10, 2024
Manipulating the polarization of light at the nanoscale is key to the development of next-generation optoelectronic devices. This is typically done via waveplates using optically anisotropic crystals, with thicknesses on the order of the wavelength. A team of researchers in the US (Stanford, SLAC Nation Acceleration Laboratory, Harvard University, Columbia University, Florida State University, UCLA) used a novel ultrafast electron-beam-based technique sensitive to transient near fields at THz frequencies to observe a giant anisotropy in the linear optical response in Tungsten ditelluride (WTe2). They demonstrated that it is possible to tune THz polarization using a 50 nm thick film, acting as a broadband wave plate with thickness 3 orders of magnitude smaller than the wavelength. The observed circular deflections of the electron beam were consistent with simulations tracking the trajectory of the electron beam in the near field of the THz pulse. According to the researchers their findings open a new approach to enable atomically this THz polarization control using anisotropic semimetals and define new approaches for characterizing THz near-field optical response at far-subwavelength length scales… read more. TECHNICAL ARTICLE
… electrons moved in a circular pattern (right) after the thin material (center) was hit with linearly polarized terahertz radiation (left). Credit: Nano Lett. 24, 20, 6031–6037, May 8, 2024