Interaction of Confined Polaritons in Microcavity Structures

A polariton is a quasiparticle formed from the coupling of a confined photon in a cavity to electronic excitation, like exciton in a semiconductor. This dissertation reports on series of experiments in confined polariton interaction by design, fabrication, and characterization of semiconductor microcavity structures operating in strong or weak coupling regime.

In the first part of the thesis, we mainly concentrate on the optical study of the 2D microcavity sample, including spin-dependent lower-upper polariton cross interactions by pump-probe spectroscopy technique, supported by theoretical analyses and numerical simulations based on Gross-Pitaevskii equations. In particular, we present a scattering resonance behavior via an exciton molecule (biexciton) when polaritons from both the upper and lower branches with anti-parallel spins are involved through a polaritonic cross Feshbach resonance. This demonstration will permit the control of the polariton interbranch scattering.

The second part of the thesis is dedicated to the design and fabrication of the potentials where the photonic part of polaritons is confined laterally by adjusting the thickness of the cavity layer locally in so-called mesa structures. By engineering a periodic lattice of mesas on a two-dimensional microcavity, it is possible to couple confined polariton modes of nearby mesas to establish an optical lattice analogous to the crystalline semiconductors’ electronic band structures. We especially demonstrate the localization of light with a lasing mode at the edge of the Brillouin zone in a two-dimensional triangular lattice. We produce a self-trapping of light by optically inducing a local breaking of the strong-coupling regime of excitons to photons. In the weak coupling regime, we control the confined modes by the shape of the generated defect. We also reveal a controllable localization degree and experimental signature of the Anderson localization in microcavity polaritons by inducing positional disorder in the triangular lattice.

The last part is devoted to the fabrication of sub-micron size mesas to enhance polariton interaction by confining them tightly and discuss the quantum correlation of polaritons by a Hanbury Brown and Twiss (HBT) setting toward polariton blockade.