2013 Dirac medal

Professor Stephen Mark Barnett, University of Strathclyde. For his wide ranging contributions throughout optics research, which both inspire and lead experimental endeavours.

Professor Barnett is one of the leading theoretical physicists in the UK today. His work has had a very great impact on our understanding of light and matter. He has made game-changing contributions to quantum optics and its application to information processing. His most famous achievement is the formulation of the phase operator for light. This was a major step, since it resolved the various different formulations that had been argued about for decades into a clear and coherent framework.

This work exemplifies Stephen Barnett’s approach to physics.  He chooses profound, unresolved questions, and then works out the definitive solution. Another, more recent, example is the resolution of the Abraham-Minkowski dilemma about the correct momentum of light in a medium, which has been disputed since 1909. Professor Barnett resolved it simply and effectively in terms of the differences between the canonical and the kinetic momentum of the photons.

Another area to which he has made key contributions is that of the orbital angular momentum of light beams. His ideas have informed and guided experiments in this area in a most fruitful manner, and he is regarded as the world’s leading theorist in this area. These are merely a few examples of the keen insight Stephen Barnett has brought to important physics problems.