Abstract
Metamaterials are composite materials composed of artificial subwavelength building blocks. By exploiting light and matter interactions, metamaterials exhibit many exotic phenomena not found in nature, and have attracted considerable research interest. Chiral metamaterialsprovide the opportunities for people to manipulate polarization of light and design new devices. In this thesis, we investigate the optical properties of metallic helix array photonic metamaterials. In the previous reports, such structure exhibits strong circular dichroism with a broadband response and can be used as circular polarizer devices. Although the optical response of helix array composite can be well described by antenna theory, the fundamental mechanism is not clear for further applications of such metamaterial. In this thesis, we propose that helix can be regarded as a composition of several units of a half-pitch helix. A hybridization model is proposed to explain the interaction among the helix units and thus the optical response. Furthermore, the response of interwined helices for broader bandwidth is also explained. Such physical picture is more comprehensive and helpful for further applications. The optical response of helix metamaterial is scalable with the dimensions due to the linearity of Maxwell’s equations. However, as the operation range approaches the optical frequencies, the plasmonic effect becomes evident and the scaling is saturated near certain frequency. Hence we also study the nonlinear scaling phenomenon at optical regime and the optical properties therein. Field enhancement and energy propagation are investigated. This study can be helpful for plasmonic applications of chiral version.