Photons, like all bosons, exhibit Bose-Einstein condensation (BEC) under the right conditions. In this talk, I will give a brief overview of how these right conditions have been achieved using an optical microcavity, leading to Bose-Einstein condensation , before reporting on more recent results pushing such condensates down to the low photon number limit . This low number limit for BEC raises questions, which I address, of how one can mark a condensation thresholds outside of the macroscopic limit.
We use focussed ion beam milling to create mirrors of near arbitrary shapes giving us a high degree of control over the dimensionality and potential landscape of our cavities, and hence the optical modes of the cavity.
I describe how our system can be fully characterised by a dynamical model, which in one limit recaptures complete thermal equilibrium behaviour, and in the other limit recaptures laser behaviour  as well as many other interesting non-equilibrium phenomena . This plays into questions of how thermal equilibrium breaks down in driven-dissipative systems.
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