Protected nanoaperture based on multi-excitation of the localized surface plasmon between a ridge nanoaperture and metal nanoparticle

To protect a ridge nanoaperture from environmental rigors and to minimize losses created by a dielectric protection layer, we developed a multiexcited nanoaperture by combining a ridge nanoaperture with an aluminum nanoparticle. We observed that the aluminum nanoparticle propagated the optical field from the nanoaperture to the exit plane via plasmon coupling, which facilitated confinement of the optical field. Additionally, even when the exit plane of the multi-excited nanoaperture was covered with a dielectric protection layer, the aluminum nanoparticle still confined the optical field in a small, localized region. The resulting spot size from a pure ridge nanoaperture, covered with a protection layer, was 166 × 86nm2 (full-width at half maximum) at a distance of 10nm from the protection layer. For the protected multi-excited nanoaperture configuration, the spot size at the full-width at half maximum was 32 × 30nm² at a distance of 10nm from the protection layer.