Improvement of plasmonic field-matter interaction by subwavelength dielectric gratings

We investigate that the detection sensitivity in surface plasmon resonance (SPR) biosensors can be significantly enhanced by employing subwavelength dielectric gratings deposited on a gold film. The enhancement is due to an improvement of field-matter interaction, i.e., enhanced evanescent field intensity at the binding region and increased surface reaction area. After a large-area SiO₂ grating fabricated by nanoimprint lithography, the sensor performance measured by parylene film shows that the SPR substrates combined with a dielectric grating provide a notable sensitivity improvement compared to a conventional bare gold film. We also find that plasmon field can be more confined and enhanced at the dielectric gratings with a larger width. The proposed SPR structure could potentially be useful in a variety of plasmonic applications including high-sensitivity biosensors.