Photonic resonators, coupled within a lattice, have appeared in the recent years as a powerful synthetic platform to imprint on light some of the fascinating physical properties that can emerge in condensed matter, or even to go beyond what exists in nature. For instance, light can become superfluid, present spin orbit coupling, spin Hall effect or propagate along topologically protected edge states [1-2].
In the present talk, I would like to discuss the influence of the openness of the system on the physics. Indeed photons constantly leak out from the cavities, so that the system needs beeing continuously pumped for a steady state to be reached. The steady state can be strongly out of equilibrium. Moreover engineering of the drive, that is injecting photons in a very controlled wat, provides a new tool to tailor the band structure and manipulate the topology of lattices.
After a general introduction to polariton lattices, I will illustrate this driven dissipative physics by presenting two of our recent experiments. First I will show how we could evidence experimentally that polariton condensates belong to a different universality class than their equilibrium counterpart, namely the Kardar Parisi Zhang (KPZ) universality class . Second, I will present how we could generate a non trivial topological interface in a lattice, using the interplay of drive engineering and non-linearity .
 C. Ciuti and I. Carusotto, Quantum fluids of light, Rev. Mod. Phys. 85, 299 (2013)
 A. Amo and J. Bloch, Exciton-polaritons in lattices: A non-linear photonic simulator, Comptes Rendus de l’Académie des Sciences 8, 805 (2016) (Elsevier)
 Q. Fontaine et al., Observation of KPZ universal scaling in a one-dimensional polariton condensate, Nature 608, 687 (2022)
 N. Pernet et al., Topological gap solitons in a 1D non-Hermitian lattice, Nature Physics 18, 678 (2022)