Interaction of transverse modes via four-wave mixing in a rubidium vapor cell inside a ring resonator: A nonlinear optical analogy to Bose-Einstein condensation

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This project focuses on the study of the transverse dynamics of a nearly-confocal nonlinear Fabry-Perot ring resonator, using a rubidium vapor cell placed in the resonator as a Kerr medium. Coupling by four-wave mixing of the transverse modes is predicted to produce a transverse cavity mode spectrum consisting of a central spike corresponding to the lowest on-axis TEM-00 mode, on top of a low pedestal of higher modes. The similarity of this transverse mode spectrum to the central spike formed by bosons in the momentum space distribution when they undergo Bose-Einstein condensation (BEC) suggests that these phenomena can also be understood by an analogy to BEC. Extending this analogy, the group will attempt to observe a BEC-like phase transition in which the well-collimated output beam corresponding to the central-spike momentum spectrum suddenly becomes uncollimated as a random modulation of the input laser light by crossed AOMs is increased beyond a certain critical amplitude.