connection symposium toronto, on may 8, 2009 meta-screen for high resolution optical microscopy yan...
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Connection Symposium
Toronto, ONMay 8, 2009
Meta-Screen for High Resolution Optical Microscopy
Yan Wang*, Amr S. Helmy, & George V. Eleftheriades
University of Toronto
Connection Symposium
Toronto 2May 8, 2009
Overview
• Background Background – Conventional optical microscope and its resolution
limit;– Development in various high resolution microscopy
technologies and their pros and cons.
• Scanning near-field optical microscopy (SNOM)Scanning near-field optical microscopy (SNOM)– Basic operating principles and drawbacks.
• Theory of meta-screenTheory of meta-screen– Improves the current SNOM resolution;– Design principles and performances;
• ConclusionConclusion
Connection Symposium Background
• Optical microscopy – seeing things with lightOptical microscopy – seeing things with light– Conventional compound optical microscopesConventional compound optical microscopes
Toronto 3May 8, 2009
An 1879 Carl Zeiss Jena Optical microscope
Mirror
Stage (with clips)
Objective Lens
Eyepiece lens
Focus
Nikon Eclipse 600 transmitted/reflected light microscope
Connection Symposium Background (cont’d)
• Resolution limit of conventional optical microscopesResolution limit of conventional optical microscopes– Abbey’s diffraction limit (200nm for the visible
spectrum)
Propagating waves: e-jβz
x
z
k0-k0
kx
Spectrum of the spatical information
Toronto 4May 6, 2010
Evanescent waves: e-αz
Connection Symposium
Toronto 5May 6, 2010
Background (cont’d) (cont’d)
• Efforts in achieving high-resolution (beyond the diffraction Efforts in achieving high-resolution (beyond the diffraction limit)limit)
• Electron microscope (TEM, SEM and REM etc.)
• Atomic force microscope (AFM)
• Pendry’s “perfect lens” (meta-material application)
Jason Palmer, BBC news, Friday, 28 August 2009, “Single molecules stunning image”
J.B. Pendry, “Negative refraction makes a perfect lens” Phys. Rev. Lett. 85, 18 (2000).
Connection Symposium SNOM
• Scanning near-field optical microscope Scanning near-field optical microscope
Toronto 6May 6, 2010
WiTech alpha300S Scanning Near-field Optical Microscope, ϋlm, Germany
Human leucocyte SPP propagation
Aperture probe limits resolution– Operates in the near-field– Does not depend on the
wavelength of the illuminating light– Suffers tremendous power loss
Connection Symposium Meta-screen
Toronto 7May 6, 2010
• Improve the focusing ability of the aperture (multi-aperture Improve the focusing ability of the aperture (multi-aperture approach)approach)– Circular aperture vs. slot aperture
– Single-slot vs. multi-slot
L. Markley et. al., “A spatially shifted beam approach to subwavelength focusing,” Phys. Rev. Lett. 101, 10 (2008).
4
transmissionr
Bethe’s diffraction theory
Slot antenna theory
Connection Symposium Meta-screen
• Multi-slot metallic transmission screen (Meta-Screen)Multi-slot metallic transmission screen (Meta-Screen)
Toronto 8May 6, 2010
Target BeamwidthTarget Beamwidth
FWHM = 0.12λ0
Transmission screenTransmission screen
Weight = 1, -1/2, 1/5, -1/10, …
yxz
x
z
Connection Symposium Meta-screen (cont’d)
• Meta-screen improves near-field focusingMeta-screen improves near-field focusing
Material: Ag (εr = -31.26-j1.14)Thickness = 40nm, Slot width = 40nmCentral slot length = 200nmSatellite slot length = 130nmSlot separation distance = /10 = 83nm
Toronto 9May 6, 2010
Y. Wang et. al., “Plasmonic meta-screen for alleviating the trade-offs in the near-field optics ”, Optics Express, 17, 12351-12361 (2009)
Magnitude of Ex (log scale) Magnitude of Ex (log scale)
Connection Symposium
Thank you!