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Researchers trying to make high-capacity DVDs, as well as more-powerful computer chips and higher-resolution optical microscopes, have for years run up against the "diffraction limit." The laws of physics dictate that the lenses used to direct light beams cannot focus them onto a spot whose diameter is less than half the light's wavelength. Physicists have been able to get around the diffraction limit in the lab--but the systems they've devised have been too fragile and complicated for practical use. Now Harvard University electrical engineers led by Kenneth Crozier and Federico Capasso have discovered a simple process that could bring the benefits of tightly focused light beams to commercial applications. By adding nanoscale "optical antennas" to a commercially available laser, Crozier and Capasso have focused infrared light onto a spot just 40 nanometers wide--one-twentieth the light's wavelength. Such optical antennas could one day make possible DVD-like discs that store 3.6 terabytes of data--the equivalent of more than 750 of today's 4.7-gigabyte recordable DVDs.
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