Vertical coupling to photonic crystal waveguide using chiral plasmonic lenses

Manipulating surface plasmon polariton waves for the development of micro-nano devices has been widely studied in recent years. Two-dimensional artificial photonic crystals have bandstructure characteristics like semiconductors. However, the requirement for light to be incident along the structural periodic direction poses a challenge in coupling light into the photonic crystal, thereby impeding its integrations and applications. In this work, we proposed coupling vertically incident left-circularly polarized light into a photonic crystal waveguide using a chiral plasmonic lens. Linearly-polarized light can also generate surface plasmon polariton waves and couple them into photonic crystal waveguides, but the intensity is lower. In contrast, right-circularly polarized light propagates in the opposite direction and exhibits minimal propagation into the photonic crystal waveguide. The results indicate that the proposed structure can operate broadband within the wavelength range of 620–670 nm. This method provides a simple and easily integrated coupling method for photonic crystal devices.