Effects of Distributed Bragg Reflectors on Temporal Stability of CuCl Microcavities

Abstract

We have investigated the characteristics of exciton polaritons in a CuCl microcavity with distributed Bragg reflectors (DBRs). Two sets of multilayers, PbBr2/PbF2 and HfO2/SiO2, were adopted as the DBRs in order to study the temporal stability of the CuCl microcavity. The thickness of the CuCl active layer was fixed to an effective 3λ/2 length. Angle-resolved reflectance spectra clearly demonstrate the formation of the cavity polaritons. From the phenomenological analysis with a 3×3 Hamiltonian for the cavity-polariton modes originating from the Z3 exciton, Z1,2 exciton, and cavity photon, the Rabi splitting energies are evaluated to be 97 and 162 meV for the Z3 and Z1,2 excitons, respectively, in the fresh CuCl microcavity with the PbBr2/PbF2 DBR. However, the Rabi splitting energies remarkably decrease within 6 days from the sample preparation, which is due to the degradation of the DBR resulting from alloying of PbBr2 and PbF2. On the other hand, in the CuCl microcavity with the HfO2/SiO2 DBR, the Rabi splitting energies of 105 and 168 meV for the Z3 and Z1,2 excitons, respectively, hardly change during 360 days from the sample preparation. This indicates that the stability of the oxide materials of HfO2 and SiO2 prevents the degradation of the DBR and CuCl active layer. Thus, a stable CuCl microcavity can be prepared by adopting the multilayer of HfO2/SiO2 as the DBR, which is a merit in applications.