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Zhuo Ying Wu High School for Dual Language and Asian Studies Professor Dr. Huizhong Xu Discussions Background Methods In this work, transmission of light through a nanoaperture was simulated by the finite element method using a commercially available software called COMSOL Multiphysics [5]. Illumination was normally incident onto a metal film through a fused silica substrate on which the metal film is situated. Inside the metal film, a nanometer-sized hole was filled with a dielectric material. The medium above the metal film is assumed to be air. A computation domain of one wavelength in all three directions is terminated by perfectly matched layers (PML) which serve as the PML boundary condition. 0.5 Three-dimensional finite element method was used to simulate transmission of light through the dielectric-filled nanoapertures. Results Normalized transmission through zincoxide-filled apertures in a 100-nm-thick silver film is plotted versus aperture diameter in Fig. 1. Here normalized transmission T is defined by the ratio of the transmitted photon flux to the incident photon flux on the aperture area: T normalized transmission Transmission of 488 nm light through zinc-oxide-filled nanoapertures of various diameters in a silver film was studied using three-dimensional finite element method. We found that transmission displays a resonance peak at an aperture diameter of around 40 nm. The normalized transmission at this peak reaches nearly 50% for a film thickness of 100 nm, and exceeds 100% for a film thickness of 60 nm. These zincoxide-filled nanoapertures may be useful for a variety of applications including optical probe devices with resolution down to 30 nm. It can be seen from Fig. 3 that transmission curves for film thicknesses of 60 nm, 100 nm and 130 nm exhibit a resonance peak at an aperture diameter around 40 nm. The peak shifts to smaller aperture diameter while the normalized transmission at the resonance increases as the film thickness decreases. 0.4 0.3 0.2 0.1 0 0 Conclusion 50 100 diameter (nm) 150 200 P dS n a 2 I 0 where is the intensity of the incident light, is the aperture radius, denotes the component of the time averaged Pointing vector along the normal to the metal film plane. The integration is performed over a circular area of covering the aperture at its exit. From Fig. 1, we can see there is a resonance peak at an aperture diameter of around 40 nm. The normalized transmission at this peak reaches 43%. The electric filed direction inside the aperture at this resonance is shown in Fig. 2. The electric field points in the same direction throughout the whole depth of the aperture. Using finite element method, we have calculated transmission of 488 nm light through zinc-oxide-filled nanoapertures with varying diameters in a silver film of various thicknesses. We found that transmission displays a resonance peak at an aperture diameter of ~ 30 nm for a 60-nm-thick silver film and ~ 40 nm for a 100-nm-thick film. The normalized transmission at this peak exceeds 100% for the 60-nm-thick film. Acknowledgements FIG. 2. Field distribution inside aperture under the same condition described in Fig. 1 for an aperture diameter of 40 nm. False colors denote the square of the norm of the electric field (normalized by the incident electric field) in a logarithmic scale. The black arrows denote electric field directions. •Dr. Huizhong Xu •Dr. Sat •Harlem Children Society and staffs •St Johns University and its staffs • My partner(Samuel Chan) •Audiences