2013 Young Medal and Prize

Professor Jeremy J Baumberg, University of Cambridge. For his pioneering contributions to nanophotonics, and in particular for demonstrating the wide variety of coherent optical interactions of semiconductors

As an outstandingly creative experimentalist in semiconductor optoelectronics and nanophotonics, Baumberg is particularly renowned for discovering stimulated scattering in semiconductor microcavities. He demonstrated the first coherent control in solids leading directly to quantum-information processing in semiconductor nanostructures, invented ultrafast optical techniques now widely used to study spintronics in semiconductors, and pioneered many novel plasmonic and periodic nanostructures.

One question Baumberg followed is, ‘how similar to atoms are the electronic excitations in semiconductors, and can they be exploited?’ Electron-hole pairs in semiconductors bind together to form excitons resembling hydrogen atoms. At Hitachi he explored the quantum coherence of excitons aiming at their coherent control to produce the fastest optical switch in the world using the phase of successive optical pulses. Previously demonstrated using atoms but unknown in solids, the community believed exciton analogues could not work. Baumberg’s techniques, now widely adopted, allow study of fundamental scattering of excitons, and form the basis of widespread developments in quantum information processing in the solid state.

Recently Baumberg developed analogues of atom-cavity QED in the solid state, in which excitons in a thin semiconductor sheet are sandwiched between two mirrors. In 2000, he discovered and explained completely new nonlinear optical properties in these multilayered samples. The exciton and photon are mixed into a new composite particle termed a polariton. He has shown that polaritons are nothing like either excitons or photons (despite being composed of half of each), but interact millions of times more strongly than excitons. His work launched a research wave, dominating many international conferences. As bosons are ten thousand times lighter than excitons, exciton-polaritons can condense into Bose-Einstein condensates even at high temperatures. Polariton lasers can be ultra-low threshold emitters of coherent radiation and very recently Baumberg demonstrated the first room-temperature polariton lasers.