Polariton parametric scattering processes in semiconductor microcavities observed in continuous wave experiments

Abstract

Novel polariton-polariton scattering processes in a III-V semiconductor microcavity are investigated under conditions of cw resonant excitation close to the point of inflection of the low polariton (LP) branch at wave vector $k_P.$ In addition to the strong emission at wave vectors near $k=0\mathrm{}$ and ${2k}_P$ occurring due to parametric polariton scattering from the excitation point on the LP dispersion, sharp peaks located off the LP branch are observed in the vicinity of ${k=3k}_P$ and $-k_P.$ We demonstrate that they arise due to additional parametric scattering between the macrofilled $k\approx 0,$ $k_P$ and ${2k}_P$ modes. Pronounced anomalous dispersion of the peak near ${k=3k}_P$ is found and shown to originate from that of the macroscopically occupied states near ${k=2k}_P.$ A surprisingly high degree of polarization of the $k\approx {3k}_P$ peak, markedly exceeding that of the excitation, is observed under excitation with elliptically polarized laser light. It is explained taking into account strong nonlinearity of the $k\approx {3k}_P$ peak emission close to the threshold. We also discuss the effect of the incoherent processes in the system, occurring at high excitation power or at temperatures above 15 K, on population of the additional modes.