Optical Properties of Excitons Strongly and Weakly Coupled to Cavity Photons.

Mukesh Kumar Samal, Divya Mishra, Parvendra Kumar

Semiconductor quantum dots are among the best sources of on-demand entangled photon pairs. The degree of entanglement, however, is generally limited by the fine structure splitting of exciton states. In this paper, we theoretically investigate the generation of polarization-entangled photon pairs under two-photon excitation and cavity-assisted two-photon emission, both in the weak and strong cavity coupling regimes. We demonstrate and clarify that cavity coupling together with an excitation pulse reduces the degree of entanglement in three different ways. First, in a strong coupling regime, the cavity introduces the unequal ac-Stark shift of horizontally and vertically polarized exciton states, which results in the effective splitting of exciton states. Second, it induces the cross-coupling between the exciton states even in the weak coupling regime, causing the creation of unfavorable two-photon states. Finally, higher excited states of the cavity modes also contribute to the reduction of entanglement. Therefore, in the setting considered here, cavity coupling, which is generally required for the efficient collection of emitted photons, degrades the entanglement both in weak and strong coupling regimes.

Smadar Ben‐Tabou de‐Leon, Boris Laikhtman

Lucio Claudio Andreani

Hashem Zoubi, Helmut Ritsch

We study the resonant electronic excitation dynamics for ultracold atoms trapped in a deep optical lattice prepared in a Mott-insulator state. Excitons in these artificial crystals are similar to Frenkel excitons in noble atom or molecular crystals. They appear when the atomic excited state linewidth is smaller than the exciton bandwidth generated by dipole-dipole coupling. When the atoms are placed within a cavity the electronic excitations and the quantized cavity mode get coupled. In the collective strong coupling regime excitations form two branches of cavity polaritons with Rabi splitting larger than the atomic and the cavity linewidth. To demonstrate their properties we calculate the transmission, reflection, and absorption spectra for an incident weak probe field, which show resonances at the polariton frequencies.

Guangcun Shan, C.H. Shek

In this work we have studied the quantum statistical properties of the photon emitted from a driven microcavity embedded with a single armchair-edged graphene nanoribbon (GNR). The system is coherently pumped with weak laser amplitude. Analytical expressions are derived in both strong and weak coupling regimes and the nonclassical proprieties of the emitted field have been investigated. Furthermore, it is concluded that this excitonic system presents several statistical similarities to the atomic system, in particular for the bad-cavity and good-cavity limits in the weak laser amplitude regime. We have shown that independently of the excitonic nonlinearity, which describes the interaction strength of the excitons in GNRs, the autocorrelation function is antibunched for an exciton cooperativity value range. More interestingly, it is demonstrated that the exciton-exciton interaction strength in GNR can be deduced from the value of the autocorrelation function at zero time delay of τ=0. Our theoretical results demonstrated that a microcavity embedded with a single GNR can serve as a nanophotonic device and a useful analysis method for a deep understanding of excitonic properties of GNRs.

Selvakumar V. Nair, T. Takagahara