Prof. Xiang Zhang's Laboratory

at UC Berkeley

Site Updated:
09/18/2008

Enhancement of Evanescent Waves using Thin Silver Slab

Objective

To verify the enhancement of evanescent waves through a thin silver slab, a superlens, thus achieving sub-wavelength resolution imaging in the nearfield.

Background

The resolution of conventional lens optics imaging such as optical microscope is limited by the diffraction of light called the diffraction limit, in the order of working wavelength. Pendry claimed (Phys. Rev. Lett. 85, 3966) that a thin silver slab acting as a superlens, can enhance the otherwise decaying evanescent waves through surface plasmon resonance and restore missing sub-wavelength information in the image plane.

Fig. 1
Fig. 2

Results

We observed the evanescent wave enhancement through a thin silver film1 (Fig.1). A band of evanescent waves scattered by random surface modulations is transmitted through the silver slab and recorded in the far field using a hemi-spherical lens. An optimal thickness exists (50nm in this experiment) due to the opposing action of loss in silver.

We also showed the imaging ability of silver through a numerical study2 (Fig. 2). Because the sub-wavelength information is carried to the image plane by enhanced evanescent waves, l/6 resolution imaging is possible with 36nm thick silver film using 365nm wavelength.

Representative Papers:

Z. Liu, N. Fang, T.-J. Yen, X. Zhang, Appl. Phys. Lett., 83, 5184 (2003) vew pdf

N. Fang, X. Zhang, Appl. Phys. Lett. 82, 161(2003) view pdf

 

 

 
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