Finite-difference time-domain study of Si nanorod arrays with UV and green light

The finite-difference time-domain (FDTD) simulation on the absorption properties of Si nanorods with different spacings at UV and green light has been conducted. It was revealed that the enhanced absorption along the sidewalls of Si nanorods occurred, parallel to the light polarization directions, at UV-light while the green light is literally confined towards the nanorod center which leads to the V-shape absorption. The significant difference in absorption profile at two different illuminations is mainly due to the distinct origin of the light-matter interactions. For the UV light, the polarization induced local electric field in the gap between nanorods is responsible for the results observed. However, the confined prolonged absorption of the green light is attributed to the non-negligible total internal reflection inside Si nanorod waveguide.