Phase Conjugation Enhanced by Weak Localization of Exciton Polaritons

Nobuhiko Taniguchi, Eiichi Hanamura

V. E. Kravtsov, Vladimir I. Yudson, V. M. Agranovich

Nobuhiko Taniguchi, Eiichi Hanamura

Eiichi Hanamura

Large, nonlinear-optical phenomena are shown theoretically to be observable under nearly two-photon resonant pumping of the excitonic molecule (EM), e.g., in a CuCl crystal. When the exciton polariton (EP) is resonantly pumped into the EM, they are hybridized with each other and show optical Stark splitting. These splittings can be observed, respectively, as a sharp dip in the reflection spectrum and two-photon absorption spectrum due to the EM. We can also clarify how these splittings change into the blueshifts and redshifts of the EP and the EM as functions of the pump frequency and power. The generation of the phase-conjugated wave is shown also to be enhanced under two-photon resonant pumping of the EM. Some characteristics about pump-probe frequency and polarization dependences are also clarified. We have also derived the effective Hamiltonian of the exciton and the EM from the first-principles equation of motion for the exciton coupled with that of the EM. This Hamiltonian has made possible the theoretical analysis of these nonlinear-optical phenomena.

Jagannath Paul, Jared K. Wahlstrand, Alan D. Bristow

Dionisis Stefanatos, Emmanuel Paspalakis

Creating sufficiently strong entanglement between exciton-polaritons is a step of utmost importance towards the exploitation of these systems in quantum information processing with continuous variables. The generation of entanglement relies on the strength of the nonlinearity, which is weak for semiconductor microcavities. Recently, a way to essentially amplify the nonlinearity strength in these systems using two coherent laser fields was suggested, leading in theory to the creation of a fair amount of entanglement between exciton-polaritons in coupled cavities and networks in general. Throughout this process, the Josephson coupling and the enhanced nonlinearity in the two coupled cavities are held constant, with the former always larger. In this work we show that the entanglement generated with the above procedure can be substantially enhanced with the appropriate on-off switching of Josephson coupling between the cavities. Furthermore, we show that if we consider a time-dependent enhanced nonlinearity, through the modulation of the corresponding coherent laser fields, and allow it to attain larger values than the Josephson coupling, then we can generate larger values of entanglement using shortcuts to adiabaticity, a method developed to accelerate quantum adiabatic dynamics. The suggested methodologies are not restricted to exciton-polaritons but are expected to find applications in a wide spectrum of physical contexts, where nonlinear interacting bosons are encountered.