Analysis of Absorptive Nickel Grating with a Dielectric Layer

Background: Nickel grating absorber has been studied and shows good absorption property in the visible band. In order to further improve the absorption performance, reflection should be reduced, and anti-reflection layer should be added upon or under the gratings. Method: In this paper, the dielectric layer is added between and upon the nickel gratings. Equivalent medium theory is used to analyze the role of dielectric layer on absorption mechanism of nickel gratings. photoresist is used to illustrate the possible practical usage of the proposed method. Results: Absorption efficiency of TM (transverse magnetic) and TE (transverse electric) polarization show growing trend with the increase of refractive index of the dielectric material. PMMA and TU7 are chosen as the dielectric material. The simulation results show that TM absorption reduced slightly in visible band, and improved by up to 86% in the near infrared region. TE absorption shows up to 79% improvement in the whole visible to near infrared waveband. Conclusion: Nickel grating based broadband absorber is analyzed in this paper. Dielectric layer is added upon the gratings, and act as the anti-reflection layer. The refractive index and layer thickness is analyzed by using equivalent medium theory. Dielectric material that has high refractive index is more desired. The designed nickel grating shows high absorption property from 450nm to 800nm for both TM and TE polarization.