Tailoring photonic crystal waveguides to create chiral fields

Abstract

In this work we present a design for a chiral photonic crystal waveguide (PhCW). This chiral PhCW was achieved by breaking all mirror symmetries of a conventional PhCW by adding an SiO2 substrate and shifting the positions of the air holes along the waveguide. The resulting chiral PhCW exhibits a non-monotonic dispersion of the fundamental mode, shifted field patterns, creation an annihilation of of circular polarization singularities, and a shift in their position. The near-fields above this chiral PhCW have an integrated optical chirality with a value that is 0.16 times that of circularly polarized light. As absorption rates and refractive index in solutions of chiral molecules are chirality-dependent, this chiral PhCW could be used as a first step towards on-chip measurements of chiral purity of solutions of chiral molecules.