Semiconductor microcavities appears today as a new platform to investigate quantum fluids of light. They enable confining in a very small volume both light and the material electronic excitations. The resulting strong light-matter coupling gives rise to the formation of hybrid light-matter quasi-particles, named excitonic polaritons.
Excitonic polaritons propagate like photons but strongly interact with their environment via their matter component: they behave as quantum fluids of light, and show fascinating phenomena like superfluidity, nucleation of topological excitations such as quantized vortices... Patterning of semiconductor microcavities on a micron scale allows confining polaritons in photonic circuits or in lattices.
After a general introduction on cavity polaritons, I will illustrate the diversity of physical problems which can be addressed using patterned microstructures. I will show that taking advantage of the strong non-linearities induced by polariton interaction, we can realize photonic circuits, in which coherent polaritons propagate and are optically manipulated.
The second part of the talk will be dedicated to the physics of polaritons in lattices. I will show that we can implement different Hamiltonians and emulate a variety of physical systems: Dirac physics in honeycomb lattices, fractal energy spectrum in a quasi-periodic potential or phase frustration in lattices holding a flatband. Finally I will that the hoping phase between neighbored sites can be tuned via interaction-induced interferences.
 Spontaneous formation and optical manipulation of extended polariton condensates, E. Wertz, et al., Nat. Phys. 6, 860 (2010)
 Realization of a double barrier resonant tunneling diode for cavity polaritons, H-.S. Nguyen et al., Phys. Rev. Lett. 110, 236601 (2013)
 All-optical phase modulation in a cavity-polariton Mach-Zehnder interferometer, C. Sturm et al., Nature Commun. 5, 3278 (2014)
 Fractal energy spectrum of a polariton gas in a Fibonacci quasi-periodic potential, D. Tanese et al., Phys. Rev. Lett. 112, 146404 (2014)
 Direct observation of Dirac cones and a flatband in a honeycomb lattice for polaritons, T. Jacqmin et al., Phys. Rev. Lett. 112, 116402 (2014)
 Spin-Orbit Coupling for Photons and Polaritons in Microstructures, V.G. Sala et al., Phys. Rev. X 5, 011034 (2015)
 Bosonic condensation in a flat energy band, F. Baboux et al., arXiv:1505.05652 (2015)