An international research team has discovered an effective method for controlling the frequency of confined light at the nanoscale in the form of phonon polaritons (nanolight; light coupled to vibrations in the crystal).
Research with nanolight based on phonon polaritons has developed considerably in recent years thanks to the use of sheet-structured nanomaterials such as graphene, boron nitride or molybdenum trioxide: the so-called polar van der Waals materials. Nanolight based on phonon polaritons is very promising because it can live longer than other forms of nanolight. However, because the phenomenon exists only in narrow frequency region within each material there are limits to the technological applications of phonon polariton based nanolight.
Now, however, an international team, led by researchers from the University of Oviedo and the Centre for Research in Nanomaterials and Nanotechnology (CINN-CSIC), together with scientist from the Basque research centers CIC nanoGUNE, DIPC, Materials Physics Center (CSIC-UPV/EHU), and international collaborators from the Chinese Academy of Sciences, Case Western Reserve University (USA), Austrian Institute of Technology, Paris Materials Centre, and University of Tokyo, has proposed a novel method that enables a broad extension in this range of working frequencies of phonon polaritons in van der Waals materials. The intercalation (insertion between the layers) of alkaline and alkaline earth atoms, such as sodium, calcium or lithium, in the laminar structure of the van der Waals semiconductor materials, such as vanadium pentaoxide, modifies its atomic bonds and consequently its optical properties.
It is expected that this intercalation method would be applicable to other van der Waals crystals, opening the door for the use of phonon polaritons in broad spectral bands in the mid-infrared domain.