title: High-temperature ultrafast polariton parametric amplification in semiconductor microcavities.
abstract: Cavity polaritons, the elementary optical excitations of semiconductor microcavities, may be understood as a superposition of excitons and cavity photons. Owing to their composite nature, these bosonic particles have a distinct optical response, at the same time very fast and highly nonlinear. Very efficient light amplification due to polariton-polariton parametric scattering has recently been reported in semiconductor microcavities at liquid-helium temperatures. Here we demonstrate polariton parametric amplification up to 120 K in GaAlAs-based microcavities and up to 220 K in CdTe-based microcavities. We show that the cut-off temperature for the amplification is ultimately determined by the binding energy of the exciton. A 5-micrometer-thick planar microcavity can amplify a weak light pulse more than 5,000 times. The effective gain coefficient of an equivalent homogeneous medium would be 107 cm-1. The subpicosecond duration and high efficiency of the amplification could be exploited for high-repetition all-optical microscopic switches and amplifiers. 105 polaritons occupy the same quantum state during the amplification, realizing a dynamical condensate of strongly interacting bosons which can be studied at high temperature.
authors.affiliation: Physics Department, Swiss Federal Institute of Technology Lausanne, PH-Ecublens, CH-1015 Lausanne-EPFL, Switzerland. Michele.Saba@epfl.ch
authors.forename: M
authors.initials: M
authors.lastname: Saba
authors.forename: C
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authors.lastname: Ciuti
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authors.lastname: Bloch
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authors.lastname: Thierry-Mieg
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authors.lastname: André
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authors.lastname: Dang
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authors.lastname: Kundermann
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authors.lastname: Bongiovanni
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authors.lastname: Staehli
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authors.lastname: Deveaud