Bose-Einstein condensate of exciton-polaritons in structured microcavities

Full text: The etch-and overgrowth technique for structuring in solid-state semiconductor microcavities provides a powerful tool for creating a photonic crystal-like potential landscape for a cavity photon. When the photon is strongly bound to an exciton in a quantum well embedded in the microcavity, the resulting exciton-polariton exhibits a confining potential whose scale is comparable with its wavelength. We present a set of experiments and a comprehensive theory of loading exciton-polaritons into a one-dimensional periodic lattice of buried mesa traps. By increasing the excitation power, we observe transition from an incoherent Bose gas to a highly nonequilibrium polariton condensate. We are also able to load the condensate into distinct energy bands by changing the size, shape, and position of the excitation beam. When high energy, weakly bound Bloch modes are excited, polaritons in the barrier region are free to propagate to the plane away from the array. These polaritons act as a source of coherent and phase-locked light-matter waves as evidenced by a formation of a Talbot pattern. Furthermore, we demonstrate that the mesa array acts as both an amplitude and phase grating. Thus the mesa arrays can act as an effective 1D flat lens for shaping a two dimensional coherent flow of polaritons. A mean-field nonlinear model of nonequilibrium polariton condensation with stochastic treatment of quantum and thermal fluctuations adequately describes our experimental observations. (author)