The diffraction limit has long been a fundamental barrier for optical imaging. The ability to improve the resolving power of optical systems has attracted considerable interest. This ever-growing interest is due to the enormous potential benefit it offers in diverse fields such as bio-imaging, data storage, and lithography. Significant efforts have been made to enhance optical resolution. As an earliest effort to improve the resolution, contact mask imaging was proposed and demonstrated. Immersion microscopy improves the resolution by increasing the refractive index of the surrounding medium; this method is limited by the availability of high index materials. Although scanning near-field optical microscopy (NSOM) provides subwavelength resolution, it does not project a whole image like a regular lens does. The optical information is collected by scanning a sharp tip in a point-by-point fashion near the surface which suffers from slow speed of serial scanning. It is often an “invasive” measurement that requires complicated post procedures for imaging reconstruction to remove the artifacts due to the tip-structure interaction. Recently, Pendry proposed an interesting “perfect lens theory” in which a left-handed material (LHM) is used to obtain super-resolution well below the diffraction limit.
KeywordsEvanescent Wave Negative Refractive Index Silver Layer Optical Transfer Function Surface Plasmon Excitation
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