Phys.org  May 4, 2023 Thin layers of in-plane anisotropic materials can support ultra confined polaritons, whose wavelengths depend on the propagation direction. Such polaritons hold potential for the exploration of fundamental material properties and the development of novel nanophotonic devices. However, the real-space observation of ultra confined in-plane anisotropic plasmon polaritons (PPs)—which exist in much broader spectral ranges than phonon polaritons—has been elusive. An international team of researchers (Spain, China, Czech Republic, UK, Germany) imaged and analyzed THz waves that propagate in the form of plasmon polaritons along thin anisotropic semiconductor platelets with wavelengths reduced by up to 65 times […]