Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Conventional surface plasmons have a wave vector exceeding that of light in vacuum, and therefore cannot be directly excited by light that is simply incident on the surface. However, we propose that a plasmonpolariton state can be formed at the boundary between a metal and a dielectric Bragg mirror that can have a zero in-plane wave vector and therefore can be produced by direct optical excitation. In analogy with the electronic states at a crystal surface proposed by Tamm, we call these excitations Tamm plasmons, and predict that they may exist in both the TE and TM polarizations and are characterized by parabolic dispersion relations.

Conventional semiconductor laser emission relies on stimulated emission of photons, which sets stringent requirements on the minimum amount of energy necessary for its operation. In comparison, exciton-polaritons in strongly coupled quantum well microcavities can undergo stimulated scattering that promises more energy-efficient generation of coherent light by 'polariton lasers'. Polariton laser operation has been demonstrated in optically pumped semiconductor microcavities at temperatures up to room temperature, and such lasers can outperform their weak-coupling counterparts in that they have a lower threshold density. Even though polariton diodes have been realized, electrically pumped polariton laser operation, which is essential for practical applications, has not been achieved until now. Here we present an electrically pumped polariton laser based on a microcavity containing multiple quantum wells. To prove polariton laser emission unambiguously, we apply a magnetic field and probe the hybrid light-matter nature of the polaritons. Our results represent an important step towards the practical implementation of polaritonic light sources and electrically injected condensates, and can be extended to room-temperature operation using wide-bandgap materials.

From a theoretical point of view, we discuss a variety of phenomena linked to the spin and polarization degree of freedom of exciton-polaritons in semiconductor microcavities. We start with linear optical effects including the optical spin Hall effect, formation of polarization vortices and ballistic propagation of polarized exciton-polaritons. Next, the interplay between spin-dependent dynamics and Bose condensation in the 2D system of microcavity polaritons is addressed. Theoretically, this many-body system of interacting particles is described by the spinor Gross-Pitaevskii equations. These equations provide a description of the time evolution of polarized polariton fields under different conditions of optical excitation as well as an understanding of the phenomena of superfluidity, multistability and hysteresis via renormalization of the dispersion of elementary excitations. The comprehension of polarization-sensitive dynamics can be made through the introduction of several effective fields of different nature acting on the polariton pseudospin. The theory of parametric scattering of exciton-polaritons is presented, using the second quantization formalism. It is found that the combination of nonlinearity and various mechanisms of spin reorientation leads to self-organization and the formation of polarized patterns such as polarization crosses, vortices and rings. The manipulation of polariton spins can lead to various applications in signal processing, including the construction of optical logic gates and spin memory elements; the creation of spin currents; and the control of polarized signal propagation in the microcavity plane. The concept of polariton neurons is discussed in this connection.