Characteristics of cavity polaritons in a CuBr microcavity
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We report the characteristics of cavity polaritons in a CuBr microcavity consisting of a λ/2-thick CuBr active layer and HfO2/SiO2 distributed Bragg reflectors: λ corresponds to an effective resonant wavelength of the lowest-lying exciton. The excitonic system of a CuBr crystal has three kinds of excitons labeled Zf, Z1,2, and Z3 in which the Zf exciton originates from a triplet state. We have investigated the dispersion relations of the cavity polaritons in the CuBr microcavity with the use of angle-resolved reflectance spectroscopy. The experimental results demonstrate the formation of four cavity-polariton branches due to the strong coupling between the Zf, Z1,2, and Z3 excitons and cavity photon. The cavity-polariton dispersions were well analyzed with a phenomenological Hamiltonian for the strong coupling. The evaluated Rabi-splitting energies are 28, 95, and 74 meV for the Zf, Z1,2, and Z3 excitons, respectively. These Rabi-splitting energies reflect the magnitudes of the oscillator strengths of the relevant excitons. Furthermore, it was confirmed that the cavity polaritons are fully stable at room temperature. We discuss the temperature dependence of the cavity-polariton energies and detuning, comparing with that of the bare exciton.