Abstract
Due to the weak signal of circular dichroism（CD） spectrum, this thesis uses finite-difference time-domain（FDTD） to simulate that enhanced optical chirality produced by plasmonic nanoantenna can improve CD signals. We present a design of plasmonic nanoantenna which has slant gap. When plasmonic nanoantenna at resonance by varying the total antenna length, the gap generates highly enhanced electric field that parallel to impinging magnetic field with a phase delay of π⁄2, lead to enhanced optical chirality. On the other hand, tuning the slant angle of the gap also has an influence on enhanced optical chirality. Thus, we can manipulate the enhancement of optical chirality by tuning the total length and the slant angle of plasmonic nanoantenna. Besides, we also show that asymmetric cross antenna can generate optical chirality above the antenna and interact with the dielectric material. We build cavity ring-down spectroscopy（CRDS） for experiment. CRDS has high sensitivity and it can combine with total internal reflection to have higher signal to noise ratio. In the future, combine CRDS with slant gap plasmonic nanoantenna or asymmetric cross antenna, we are able to obtain enhanced circular dichroism by linearly polarized light instead of circularly polarized light.