St Andrews ‘beams’ into world’s top 30

Wednesday 20 December 2006

A discovery made by a team of physicists from University of St Andrews has been recognised as one of the World’s top 30 optics results in 2006.

The discovery, in collaboration with researchers in the USA and Mexico, that white light can be made to behave in the same way as laser light, has opened up new possibilities for sorting cells, 3D microscopy and medical imaging.

The work of an international team led by Dr Tom Brown, of the School of Physics and Astonomy at St Andrews, has been nominated as a top discovery this year by the specialist magazine ‘Optics and Photonics News’.

Isaac Newton first showed that white light was made up of a spectrum of colours in the 17th Century. By using a prism he separated the colours, resulting in a rainbow-like effect. With the development of the laser in 1957, however, scientists had a source of light they could control and manipulate in ways that were impossible with white light. The use of lasers to move and manipulate living cells has revolutionised the field of medical research, however use is limited because laser light only contains one colour.

The St Andrews’ team worked with a device based on recent developments in nanotechnology to produce a white light beam that shares many of the properties of a laser. By taking the output from such a white light laser, they have shown that its properties can be altered in the same ways as a normal single-colour laser. At the heart of their discovery is a line of pure white light that, whilst only a few thousandths of a millimeter in diameter, can travel for distances of several centimeters. Surrounding the white focal line is a beautiful set of rainbow-like rings of many colours arising from the same behaviour that Newton observed more than 300 years ago.

The next step will be to put these white light beams to work. The St Andrews group have already shown that it is possible to pick objects up and move them through a full rainbow range of colours.

Dr Brown said, “This is important as when sorting cells scientists look for a response when a particular colour is incident – we now have a way to have every colour present without requiring the many different lasers that other approaches have used. Another area of great potential is in medical imaging where a technique called optical coherence tomography can be used to provide images from within the body using light rather than x-rays. Using white light here will enable a high degree of precision to be achieved building accurate 3D reconstructions of tissue.”

The team of researchers involved in the project are Pascal Fischer, Tom Brown, Wilson Sibbett, Jill E. Morris, Antonia E. Carruthers and Kishan Dholakia (all University of St Andrews), with collaborators in the USA and Mexico Ewan M. Wright and Carlos López-Mariscal.



For further information contact: Dr Tom Brown, [email protected]




White light – A structured white light beam. The centre is pure white light and the surrounding rings are coloured due to the composition of the white light beam.

White light rainbow – The make up of a structured white light beam – some of the different colours involved can be seen in the quadrants.

Issued by Beattie Media – on behalf of the University of St Andrews

Contact Gayle Cook, Press Officer on 01334 467227 / 462529, mobile 07900 050 103, or email gec3@st-

Ref: white light top 30 211206.doc

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