Abstract
Chiral photonic nanostructures provide a variety of fascinating properties, such as strong optical activity and circular dichroism, which can be applied in many optoelectronic devices. Although chiral motifs can be constructed by a variety of arrangements, the helix geometry is still an ideal model system to elucidate the interaction of circularly polarized (CP) light with a chiral medium. Dielectric helix structures have been studied for decades and the experimental implementation has been realized on various platforms, such as glancing angle deposition (GLAD), direct laser writing (DLW), and holographic lithography. However, these studies are predominately focused on presenting the existence of gaps, without addressing the underlying mechanisms. In this study, we use an analytical model adapted from liquid crystal and the numerical simulation based on FDTD to study the emergence and evolution of both Bragg resonance and hybridization phenomenon in a 3D dielectric helix structure. We show that the interplay of gaps with different mechanisms gives rise to versatile scenarios. We also provide a diagram that illustrates the scenarios with respect to different geometrical parameters. Such 3D configuration provides another degree of freedom to tailor the relative position between the two bands by geometrical parameters without the use of high-permittivity dielectrics, opening a new horizon to design optical devices.