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Alexey Kavokin

Professor Alexey Kavokin

Research Fellow

Organisation

University of Southampton

Research 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.

Interests and expertise (Subject groups)

Grants awarded

Scheme: Leverhulme Trust Senior Research Fellowship

Dates: Oct 2011 - Oct 2012

Value: £39,515

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