Textured Aperture Beats Diffraction
According to the theory of diffraction, an aperture strongly suppresses the transmission of light through it as its diameter falls to half the wavelength. Moreover, the transmitted light will be highly divergent. An international team working with scientists at Université Louis Pasteur in Strasbourg, France, however, has discovered that light can beat the diffraction limit if the aperture is surrounded by a periodic texture on both sides.
The researchers, who published their findings in the Aug. 2 Science, used focused beams of gallium ions to mill circular patterns around 250-nm-diameter holes and grooves around 40-nm-wide slits in 300-nm-thick films of silver. The patterns boosted transmission of red wavelengths by up to a factor of 10 and reduced angular divergence to ±3°.
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