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Second-order Coherence in an Exciton-Polariton Laser: A Quantum Monte Carlo Wavefunction Approach
Hiromi Ezaki and Yoshihisa Yamamoto

A second-order coherence function g (2)(0) is calculated in the time domain by the quantum Monte Carlo wavefunction method for an exciton-polariton laser in a semiconductor microcavity. The second-order coherence function is equal to g (2)(0) =1 at below laser threshold, takes maximum g (2)(0) ~ 1 .8, near threshold,and decreases slowly toward g (2)(0) = 1 at well above threshold,this agrees with the recent experimental result [1 ]. The polariton number and phase distribution functions calculated by the quasi-probability density Q (a) function suggest that the established quantum state is not a coherent state but a linear superposition state with an even number of polaritons. This unique state is produced by the so-called Bogoliubov couplings between the ground state and the excited states. This interpretation is supported by the positive correlation observed in the two excited states with opposite in-plane wavenumbers ±k above threshold.

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