Control of exciton-photon interactions in CuCl microcavities

Abstract

We have investigated the active-layer-thickness dependence of exciton-photon interactions in planar CuCl microcavities with HfO 2 /SiO 2 distributed Bragg reflectors. The active layer thickness was changed from λ/32 to λ/4, while the cavity length was fixed at λ/2. We performed angle-resolved reflectance measurements and clearly detected three cavity-polariton modes, originating from the lower, middle, and upper polariton branches, in a strong-coupling regime of the Z 3 and Z 1,2 excitons and cavity photon. The incidence-angle dependence of the cavity-polariton modes was analyzed using a phenomenological Hamiltonian for the strong coupling. It was found that the interaction energies of the cavity-polariton modes, the so-called vacuum Rabi splitting energies, are systematically controlled from 22(37) to 71(124) meV for the Z 3 (Z 1,2 ) exciton by changing the active layer thickness from λ/32 to λ/4. The active-layer-thickness dependence of the Rabi splitting energy is quantitatively explained by a simple theory for quantum-well microcavities.

Temperature dependence of cavity-polariton energies in ZnO and CuCl microcavities

“…The three reflectance dips are attributed to the LPB, MPB, and UPB in order of energy. Figure 2(b) shows the incidence-angle dependence of the energies of the three reflectance dips (solid circles, squares, and triangles) and the fitted results (solid curves) to the experimental data using a phenomenological Hamiltonian for the strong coupling given by the following 3 Â 3 matrix: 14,15 FIG . 1.…”

“…1 Strong coupling between the exciton and the cavity photon results in the formation of cavity polaritons. Recently, wide-gap semiconductors such as GaN, 2-7 ZnO, [8][9][10][11][12][13] and copper halides [14][15][16][17] have been adopted as active layers of microcavities from the viewpoint of the stability of excitonic systems, which is advantageous to realizing Bose-Einstein condensation of cavity polaritons 7 and polariton lasing. 5,6,13 In our previous works, we precisely investigated the characteristics of the cavity polaritons in the ZnO (Refs.…”

“…5,6,13 In our previous works, we precisely investigated the characteristics of the cavity polaritons in the ZnO (Refs. 10 and 12) and copper halides [14][15][16][17] microcavities and demonstrated the control of the exciton-photon interactions energies, the so-called vacuum Rabi splitting energies, by changing the active-layer thickness in CuCl microcavities. 15 In the microcavities, it is expected that the strong exciton-photon coupling changes the temperature dependence of the energies of the cavity polaritons from that of the bare exciton, which is an important issue in applications of microcavities.…”

Polariton dispersion relations under condensation in a CuBr microcavity

“…The bosonic properties have attracted much attention in Bose-Einstein condensation and polariton lasing from polariton condensates [1]. Recently, wide-gap semiconductors such as GaN [2][3][4], ZnO [5][6][7][8][9][10], and copper halides (CuCl [11], CuI [12], and CuBr [13,14]) have been adopted as the active layers because the excitons have large binding energies leading to high thermal stability of the cavity polariton. In our previous works on copper halide microcavities [11][12][13][14], we demonstrated giant Rabi splitting energies of the order of 100 meV and room-temperature stability of the cavity polaritons.…”

Study of exciton-polariton modes in nanocrystalline thin films of CuCl using reflectance spectroscopy

“…[4][5][6] Previous studies of CuCl using reflectance have been performed either on bulk material 7 or CuCl microcavities. 8,9 The purpose of this paper is to report low temperature reflectance spectroscopic data from thin CuCl films on (100) Si substrates and to model the exciton-polariton structure underlying such phenomena.…”