World's thinnest lens becomes reality

Washington: A team of researchers has developed the world's thinnest lens, which is one two-thousandth the thickness of a human hair, paving way for flexible computer displays and a revolution in miniature cameras.

Lead researcher Dr Yuerui (Larry) Lu from The Australian National University (ANU) said the discovery hinged on the remarkable potential of the molybdenum disulphide crystal, adding that this type of material is the perfect candidate for future flexible displays.

Lu noted, "We will also be able to use arrays of micro lenses to mimic the compound eyes of insects."

The 6.3-nanometre lens outshines previous ultra-thin flat lenses, made from 50-nanometre thick gold nano-bar arrays, known as a metamaterial.

Dr Lu said that Molybdenum disulphide, which is an "amazing crystal," survives at high temperatures, is a lubricant, a good semiconductor and can emit photons too. The capability of manipulating the flow of light in atomic scale opens an exciting avenue towards unprecedented miniaturisation of optical components and the integration of advanced optical functionalities.

The team created their lens from a crystal 6.3-nanometre thick - 9 atomic layers - which they had peeled off a larger piece of molybdenum disulphide with sticky tape. They then created a 10-micron radius lens, using a focussed ion beam to shave off the layers atom by atom, until they had the dome shape of the lens.

The team discovered that single layers of molybdenum disulphide, 0.7 nanometres thick, had remarkable optical properties, appearing to a light beam to be 50 times thicker, at 38 nanometres. This property, known as optical path length, determines the phase of the light and governs interference and diffraction of light as it propagates.

This study is published in the Nature serial journal Light: Science and Applications.