Wednesday, March 23, 2011

Lens provides sub-100 nanometer resolution with visible light

March 23, 2011

Researchers at the University of Twente in The Netherlands have developed a frosted lens that provides sub-100 nanometer resolution at visible wavelengths, says Allard Mosk.

Using a 561 nanometer laser with a flat slab of gallium phosphide, acid-etched on one side, the researchers were able to image gold nanoparticles 97 nanometers wide.  With visible light, the limit is about 200 nanometers, about the size of a measles virus.

The slab is etched in a way that entirely scatters the light that passes through it. A light wave hits the etched surface and is sent through a spatial light modulator that distorts the light in such a way that the scattering layer causes it to come to a focus.  The focal point is much tighter than can be achieved with an ordinary lens that relies on refraction alone, allowing higher resolution.

The equipment is so precise that it can control exactly where the focal point appears and can even move it around. This allows an image to be built up by scanning the focal point back and forth across the object under investigation to build up a 2D image.

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