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Register a new userOn the remote coherence of polariton condensates in 1D microcavities: a photoluminescence study
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Added by
Maria Dolores Mart\\'in Fernandez
Publication date
2020
fields
Physics
and research's language is
English
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In this manuscript we will gather clear experimental evidences of remote coherence between two polariton condensate droplets that have never overlapped in real space and discuss how these interferences in momentum space can be used to estimate the critical temperature for the BEC like transition.
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We present a time-resolved study of energy relaxation and trapping dynamics of polariton condensates in a semiconductor microcavity ridge. The combination of two non-resonant, pulsed laser sources in a GaAs ridge-shaped microcavity gives rise to profuse quantum phenomena where the repulsive potentials created by the lasers allow the modulation and control of the polariton flow. We analyze in detail the dependence of the dynamics on the power of both lasers and determine the optimum conditions for realizing an all-optical polariton condensate transistor switch. The experimental results are interpreted in the light of simulations based on a generalized Gross-Pitaevskii equation, including incoherent pumping, decay and energy relaxation within the condensate.
We examine the photoluminescence of highly-excited exciton-polariton condensates in semiconductor microcavities. Under strong pumping, exciton-polariton condensates have been observed to undergo a lasing transition where strong coupling between the excitons and photons is lost. We discuss an alternative high-density scenario, where the strong coupling is maintained. We find that the photoluminescence smoothly transitions between the lower polariton energy to the cavity photon energy. An intuitive understanding of the change in spectral characteristics is given, as well as differences to the photoluminescence characteristics of the lasing case.
Several mechanisms are discussed which could determine the spatial coherence of a polariton condensate confined to a one dimensional wire. The mechanisms considered are polariton-polariton interactions, disorder scattering and non-equilibrium occupation of finite momentum modes. For each case, the shape of the resulting spatial coherence function g1(x) is analysed. The results are compared with the experimental data on a polariton condensate in an acoustic lattice from [E. A. Cerda-Mendez et al, Phys. Rev. Lett. 105, 116402 (2010)]. It is concluded that the shape of g1(x) can only be explained by non-equilibrium effects, and that ~10 modes are occupied in the experimental system.
One-dimensional polariton condensates (PoCos) in a photonic wire are generated through non-resonant laser excitation, by which also a reservoir of background carriers is created. Interaction with this reservoir may affect the coherence of the PoCo, which is studied here by injecting a condensate locally and monitoring the coherence along the wire. While the incoherent reservoir is mostly present within the excitation laser spot, the condensate can propagate ballistically through the wire. Photon correlation measurements show that far from the laser spot the second order correlation function approaches unity value, as expected for the coherent condensed state. When approaching the spot, however, the correlation function increases up to values of 1.2 showing the addition of noise to the emission due to interaction with the reservoir. This finding is substantiated by measuring the first order coherence by a double slit experiment, which shows a reduced visibility of interference at the excitation laser spot.
We investigate an optically trapped exciton-polariton condensate and observe temporal coherence beyond 1~ns duration. Due to the reduction of the spatial overlap with the thermal reservoir of excitons, the coherence time of the trapped condensate is more than an order of magnitude longer than that of an untrapped condensate. This ultralong coherence enables high precision spectroscopy of the trapped condensate, and we observe periodic beats of the field correlation function due to a fine energy splitting of two polarization modes of the condensate. Our results are important for realizing polariton simulators with spinor condensates in lattice potentials.
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