Ni subwavelength grating/SiO2/Ag based optical magnetic field sensor with normal incident geometry

A sensitive optical magnetic field sensor was experimentally demonstrated using Ni-subwavelength grating (SWG) combined with a SiO2/Ag plasmonic structure. We fabricated the Ni-SWG structure on the Ag/SiO2 structure using electron beam lithography and a liftoff process. As a result, a dip in the reflection spectra with normal incidence was obtained at a wavelength of 530 nm. The reflectivity at the dip position significantly decreased with the intensity of the magnetic field applied to the structure. When a magnetic field of 43 mT was applied, the change in reflection reached approximately 4% of that without magnetic field. The experimental results indicate that our sensor achieves millitesla order of sensitivity for the magnetic field. The electromagnetic field distribution around the Ni-SWG/SiO2/Ag calculated using the finite-difference time-domain method clarified the reason for the high sensitivity of our sensor.

Yuusuke Takashima, Kouhei Moriiwa, Masanobu Haraguchi, Yoshiki Naoi, "Ni subwavelength grating/SiO2/Ag based optical magnetic field sensor with normal incident geometry," Proc. SPIE 11089, Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVI, 110891V (3 September 2019); doi: https://doi.org/10.1117/12.2529017

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