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Flat-plate lens achieves negative refraction, produces resolution of 100nm or finer
AIST Innovations
Experiments with holograms have led to a thin-film flat-plate lens that has a periodic (layered) structure and that is capable of a resolution of 100nm or finer. No other current lens system can do this. Because of its layered, thin-film construction, the flat lens provides excellent image-forming characteristics by the incidence of light having a wavelength slightly shorter than the wavelength corresponding to the frequency period of the thin film.
The periodic, thin-film structure can exhibit a negative refractive index at high angles of incidence. Detailed studies have been performed on the relationship between the periodic structure and the wavelength, distance between the light source and the flat-plate lens, and the image-formation characteristics of the overall optical system.
This AIST lens technology exhibits uniform performance in image-formation all over the lens surface. The thin film of the periodic structure is formed by alternate laminations (and pluralities of laminations) of two materials having different refractive indices, such as a combination of MgF2 and ZnS. The technology also provides for optical recording in high density when the lens is inserted into the optical path leading to the recording layer from a light source. Applications include high-density optical digital data recording and retrieval, and other applications demanding fine resolution or negative refractive index.
The invention evolved from hologram research. The inventors have continued extensive investigations to develop a lens by utilizing the image-regenerating characteristics of holograms as a part of their comprehensive studies in the field of optical information recording methods capable of recording and retrieving high-density information. The inventors have conducted detailed studies on the relationship between the periodic structure and the wavelength, distance between the light source and the flat-plate lens, and the image-forming characteristics thereof.
During research, the inventors discovered that, at high angles of incidence, the AIST flat-plate lens can achieve a negative refractive index, thus in theory allowing imaging smaller than that of the wavelength of light it is using. Only exotic materials have been able to achieve negative refractive indices previously.
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