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Transmission of Light through Dielectric-Filled Nanoapertures. By: Samuel Chan Zhuo Ying Wu. Mentor: Dr. Xu. St. John’s University, August, 2009. Outline. Motivation. Introduction to Dielectric-filled Nanoapertures. Previous Results. Current Work. Conclusion.
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Transmission of Light through Dielectric-Filled Nanoapertures By: Samuel Chan Zhuo Ying Wu Mentor: Dr. Xu St. John’s University, August, 2009
Outline • Motivation • Introduction to Dielectric-filled Nanoapertures • Previous Results • Current Work • Conclusion
Motivation: The Diffraction Limit a. The Image of a Point Source b. The Illumination Profile • Point spread Function (PSF) depends on numerical aperture and wavelength. • Typical PSF (NA~1, 780 nm):1 micron by 0.5 microns.
Metal-coated fiber R. C. Dunn, Chem. Rev. 99, 2891 (1999). resolution: /5 Metal tip Excitation volume E. J. Sanchez et al., Phys. Rev. Lett. 82, 4014 (1999). N. Fang et al., Science 308, 534-537 (2005). Focal volume resolution: /4 resolution: /10 Objective lens Laser illumination Motivation: Break the Diffraction Limit Resolution ~
Schematic of Light Transmission through an Aperture Metal Substrate simulation 3-D finite element method with perfectly matched layer B.C. Illumination
COMSOL Multiphysics RF Module A finite element method (FEM) software package for various physics and engineering applications, especially coupled phenomena, or multiphysics.
a-Si Au Fused Silica Illumination Fabry-Perot Interferometer Previous Results: Resonant Transmission Film thickness: 200 nm = 810 nm phase shift
-5 -4 -3 -2 -1 0 1 2 Fabry-Perot Resonances inside Waveguide phase shift = 2 phase shift = 4 200 nm 55 nm 105 nm Black arrows: electric field directions H. Xu et al., Opt. Commun. 282, 1467-1471 (2009).
ZnO Ag Fused Silica Illumination Current Work: Transmission through ZnO-filled nanoapertures in silver Film thickness: 100 nm = 488 nm Previous work: silicon-filled aperture in gold nSi: 3.882-0.099*i nAu: 0.157-4.991*i Current work: ZnO-filled aperture in silver nZnO: 2.06 nAg: 0.131-2.81*i
Phase = 0 Transmission through ZnO-filled nanoapertures in silver Hole depth: 200 nm Normalized Transmission Diameter (nm)
Transmission through ZnO-filled nanoapertures in silver with various thickness Normalized Transmission Diameter (nm)
-4 -3 -2 -1 0 1 Application: Nanoscopic Near-field Probe core 30 nm metal Si Aluminum coating tapered fiber SiO2 Illumination at 488 nm Enhancement in near-field intensity ~1000 times by silicon filling!
Conclusion • Transmission resonance peaks were found at aperture diameter of around 40 nm for ZnO-filled nanoapertures with normalized transmission of ~ 100%. • ZnO-filled nanoapertures may be useful for optical scanning probe devices that yield resolution of less than /10.
Acknowledgements Dr. Huizhong Xu St. John’s University and staff Dr. Sat Bhattacharya Harlem Children Society All of you!!