| Summary: | 碩士 === 國立交通大學 === 照明與能源光電研究所 === 99 === Microcavities containing excitons that couple strongly to photon can enter a regime of strong coupling which produces new mixed quasi-particles, the polaritons. Polaritons are half-light and half-matter particles, and possess unique and tunable dispersion relations. Recently, the discoveries in semiconductor microcavities have been shown that these polaritons differ completely from excitons in their enormous nonlinear scattering cross-sections and their bosonic statistics. This can lead to polariton lasing, the spontaneous emission of coherent light by condensates of exciton-polaritons. Unlike conventional lasers, polariton lasers have no threshold condition linked to the inversion of the population. In this thesis, a systematically study the characteristics of polariton lasers in ZnO-based Microcavities has been obtained.
First, by using angle-resolved photoluminescence measurement, dispersion curves of polariton at room temperature are observed. These experimental results agree with simulated ones from transfer matrix method. That is an evidence of the existence of polaritons.
As pumping power increases, lower polaritons efficiently relax toward ground state as a result of the increase of polariton-polariton scattering rate. When the carrier density reaches the threshold of bosonic final state stimulated scattering, lower polaritons macroscopically occupy ground state and spontaneously emit coherent light. Furthermore, we measure polarization, real space distribution, and spatial coherence in order to study the characteristics of polariton laser.
Finally, we also observe the photon lasing at different region. By comparing polariton lasers with photon lasers, the clear discrimination of dispersion curves and polarization have been shown.
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