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Alexey Kavokin

Professor Alexey Kavokin

Professor Alexey Kavokin

Research Fellow

Interests and expertise (Subject groups)

Grants awarded

Scheme: Leverhulme Trust Senior Research Fellowship

Organisation: University of Southampton

Dates: Oct 2011-Oct 2012

Value: £39,515

Summary: The word ‘laser’ originally stood for ‘light amplification by stimulated emission of radiation.’ In polariton lasers, the radiation is emitted spontaneously, but it possesses all the characteristic properties of laser light: it is coherent in the first and second order and monochromatic. The concept of polariton lasers was formulated by Imamoglu and coauthors in 1996. They are based on a type of quasiparticle called exciton-polaritons, which are made of light and matter and occur in suitably designed semiconductor crystal structures. Exciton-polaritons arise from interactions between excitons (neutral quasiparticles formed from bound electron-hole pairs) and photons (for instance, modes of visible light trapped in a semiconductor structure). Being bosons, exciton-polaritons can form condensates, similar to the Bose-Einstein condensates observed in gases of cold atoms. These condensates, in which large quantities of exciton-polaritons accumulate in a single quantum state, form the basis of the polariton laser. The exciton-polariton lifetime is shorter than a nanosecond, and they decay by passing their energy to photons, which escape from the crystal. Being generated by identical exciton-polaritons, these emitted photons form monochromatic, coherent light. Polariton lasers have been realized in semiconductor microcavities: multilayer crystal structures in which light confined between two parallel mirrors strongly interacts with the elementary excitons in the crystal. Polariton lasers will bring fundamental effects of many-body quantum physics to our everyday life. Their unique physical properties make them suitable for novel types of spin switches and terahertz lasers, which have many applications. The most promising materials for polariton lasing are the wide-band gap semiconductors GaN and ZnO, which allow for room temperature action. We are working toward realisation of optical integrated circuits based on polariton lasers.

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