Optimizing Transmission of Light Through Dielectric-filled Nano-apertures by Tuning the Index of Refraction of the Substrate
Huizhong Xu, St. John’s College of Liberal Arts and Sciences, Department of Physics
Abstract: It is well known that light cannot pass through tiny holes that are smaller than its wavelength. However, behavior of light on the nanoscale can be drastically different. We have previously found that optical transmission through a dielectric-filled nanoaperture can be greatly enhanced when a particular relationship between the dielectric constants of the cladding and filling materials at the incident wavelength is satisfied. Our recent results indicate that extraordinary transmission of more than 100% can be achieved through aperture sizes of less than one tenth of the incident wavelength by tuning the index of the refraction of the substrate on which the nanoaperture is situated. Under such conditions, a normalized near-field intensity ratio of more than 10 at the exit is also obtained. In addition, we have found that transmission also depends on the medium on the exit side. For a particular nanoaperture design, we have found transmission reaches maximum when the index of refraction of the exit medium is around 1.34, which is a perfect match to the aqueous environment in most biological applications. The strong localized nanoscopic illumination obtained in our studies can be very advantageous in a wide variety of applications ranging from biomedical engineering to information technologies.