Researchers from Fusain University and the Chinese National University of Defense Technology demonstrated that 2D all-dielectric PhC slabs without in-plane inversion symmetry can be used to efficiently separate valley exciton emission of a 2D WS2 monolayer in the far field at room temperature.

PhC slabs C4 symmetry and WS2 PL image

Left: PhC slabs with C4 symmetry and without in-plane inversion symmetry. By breaking the in-plane inversion symmetry, the polarization states of PhC can cover entire Poincaré sphere's two poles. Right: Illustration of photoluminescence of WS2 monolayer on the PhC slab without in-plane inversion symmetry.

This is the first report of effective valley separation in TMDCs by using PhCs. This method could be extended to manipulate valley exciton emission of other TMDCs monolayers. The ability of this PhC slabs to transport valley information from the near field to the far field would help to develop photonic devices based on valleytronics.