Polarization Dependence of Near-infrared Absorption Spectrum of Si-deposited Gold Nano-grating Structures

Abstract

For applications of plasmonic structures to high performance sensors in the near-infrared region, the structures require narrowband absorption peaks, good controllability of absorption peak position, and easy fabrication process. Multiple patterns with different absorption peaks should be integrated on the same substrate. In addition, polarization independence is desired for cost reduction and miniaturization of devices. In this study, we fabricated the Si-deposited gold nano-grating structures, the wire and concentric ring structures. Then their absorption spectra were evaluated. The peak wavelength shifted to longer wavelength with increasing the pitch of the grating structure and the thickness of Si. It was revealed that the peak was greatly shifted changing the thickness of Si. In the wire structures and the concentric ring structures, polarization dependence and polarization independence of peak absorption were observed, respectively. By using the Si-deposited gold nano-grating structures, wide control of the peak wavelength was realized in the near infrared region.