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Optical Mask Could Improve Imaging Resolution

Super-resolution imaging method breaks diffraction limit without using evanescent waves

by Celia Henry Arnaud
February 16, 2009 | A version of this story appeared in Volume 87, Issue 7

Researchers in the U.K. have proposed a super-resolution optical imaging method that doesn't require evanescent waves, which are light waves that decay exponentially with distance and require the sample to be very close to the imaging probe (Nano. Lett., DOI: 10.1021/nl9002014). Some imaging methods, such as scanning near-field optical microscopy that is used to scrutinize material surfaces, depend on evanescent waves. But the ability to obtain high-resolution images of objects far from the imaging device is important for biomedical imaging. Nikolay I. Zheludev and Fu Min Huang of the University of Southampton, in England, propose that longer range super-resolution imaging is possible by using an optical mask to create hot spots of concentrated light called superoscillations and to focus objects at distances beyond those reached by evanescent fields. The researchers developed an algorithm to design masks that generate hot spots of any desired size and distance from the mask. Practical applications of the masks will require manufacturing tolerances of 10% of the wavelength of light being used, the researchers say. That will be a challenging proposition for the infrared and visible regions of the electromagnetic spectrum, they add, but it should be possible with currently available techniques.


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