Jilong Bao

Light absorption enhancement of amorphous silicon film coupled with metal nanoshells

Increasing the light absorption in the weakly absorbing near-bandgap region is of great significance for improving efficiency in a thin-film silicon solar cell. In this study, light absorption enhancement near the infrared domain was realized by coating Ag nanoshells on the front side of amorphous silicon film. Detailed investigations prove that the enhancement can be related to the excitation of localized surface plasmons (LSPs). LSP scattering-induced light coupling in the guided mode, intense in-phase interference between the scattering field and the transmitted field, and the Floquet mode were observed in the simulated E-field profile, and the significant absorption enhancement was accounted for by these effects.

Metal semishell-substrate coupled structures with enlargened near-field enhancement area

Metal antennas-substrate coupled structures have unique features of strong nanoscale light confinement and field enhancement at the gap, which make them attractive and promising in a variety of applications such as sensing, lasing, and solar cell. Here, we built a coupled system consisting of a gold spherical semishell antenna and gold substrate. Through numerical simulation, it is found that due to the unique geometric shape of the antenna, the near-field enhancement area of the localized resonance is enlarged dramatically in the designed plasmonic structure, which is beneficial to increasing the active region, allowing more molecular adsorbed and also replaced easily. Moreover, the far-field extinction spectra of the localized dipole mode in the designed structure has higher quality factor and is more robust to the gap separation than its solid counterpart, which may relax the fabrication tolerances.

Role of dielectric film in metal grating for improved polarized transmittance in 0.9–1.7 µm range

It is found that the TM light transmittance and polarized extinction ratio in the near infrared range (0.9–1.7 µm) can be greatly increased by incorporating a dielectric layer between metal gratings (MGs) and high refractive index substrate (InP). The role of the dielectric layer and the physical mechanism of the polarized transmittance improvement are elucidated based on numerical simulation. Besides anti-reflection role as it is known to all, the incorporated dielectric layer is found eliminating energy losses from the Rayleigh anomalies and surface plasmon (SP)-cavity mode between adjacent metal grids. By optimizing the refractive index and thickness of the dielectric layer, it is demonstrated that the TM transmittance at the central wavelength (1.3 µm) can reach above 95% for Au MG with the period as large as 400 nm.