Driven-dissipative Bose-Einstein condensation of just a few photons

Benjamin T. Walker

Published May 1, 2020• 0 citations

Abstract

Through trapping light in a dye-filled optical microcavity, one can engineer a gapped band structure for photons, causing them to behave as massive bosons moving in two dimensions. Repeated absorption and emission by the dye can lead to a thermal distribution and Bose- Einstein condensation. In this thesis, I study photonic condensates beyond the equilibrium thermodynamic Bose-Einstein condensation limit in three ways. First, I describe a method for fine control of the trapping potential for light allowing for future study of thermalised light in box potentials and 1D potentials as well as others, expected to show quasi-condensation and possibly superfluid behaviour, rather than ideal Bose-Einstein condensation. Second, I show how this fabrication technique has been used to define tight trapping potentials with only a few thermally accessible energy levels. In these systems, dominance of the ground- state population and build-up of coherence occur at photon numbers less than ten, raising interesting questions about how to define condensation. I discuss these questions through the relevant chapter. Third, pulsed-pump experiments show interesting temporal dynamics including jitter in the formation time of a condensate after a pump pulse due to the stochastic nature of the emission processes involved. I show how the non-stationary two-time correlation function g(2)(t1, t2) is a powerful tool for characterising these temporal dynamics and I interpret the results in a more general framework of the evolution of a probability density function through an effective free energy landscape, driven by drift terms and stochastic forces.

DOI: 10.25560/82295

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