Longitudinal optical phonon assisted polariton laser

Maragkou, M., Grundy, A. J. D., Ostatnicky, T. and Lagoudakis, P. G. (2010) Longitudinal optical phonon assisted polariton laser. Applied Physics Letters, 97 (11). (doi:10.1063/1.3488012).

Abstract

We demonstrate the role of longitudinal optical (LO)-phonon assisted polariton relaxation in reducing the stimulation threshold in strongly coupled microcavities. When the energy of the relaxation bottleneck is one LO-phonon above the ground polariton state, we observe a tenfold improvement of the polariton relaxation rate in the linear regime, and a twofold reduction in the threshold to the nonlinear polariton lasing regime.
Microcavity polaritons are quasibosons that result from the strong-coupling of cavity photons and excitons confined in a single nanostructure.1 Their bosonic nature gives rise to a plethora of nonlinear phenomena2,3 epitomized by the quantum phase transition to nonequilibrium Bose–Einstein condensation.4–6 The lifetime of polariton condensates is limited to the cavity-photon lifetime leading to the radiation of directional, coherent light, termed polariton laser.7 Unlike conventional lasers, polariton lasers do not require population inversion and have the potential to operate with reduced thresholds. To date, polariton lasers have only been realized under optical excitation in microcavities with GaAs,8 CdTe,9 and GaN (Ref. 10) active material. Although electrical pumping in polariton light emitting diodes was achieved both in inorganic and organic microcavities,11–13 polariton lasing remains elusive under electrical carrier injection. As with nonresonant optical excitation schemes, so with electrical injection relaxation bottleneck leads to substantial homogeneous broadening and loss of strong coupling in the linear regime.

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Contributors

Author: P. G. Lagoudakis

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