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

本项目主要研究近共焦非线性法布里-珀罗环谐振腔的横向动力学特性，在腔内放置一个Rb蒸汽盒作为克尔介质。通过横模的四波混频耦合，预计将产生一个横向腔模谱，该谱由一个中心尖峰组成，该尖峰对应于轴上最低的TEM00模，位于较高模的低基座的顶部。当玻色子经历玻色-爱因斯坦凝聚(BEC)时，这种横向模谱与玻色子在动量空间分布中形成的中心尖峰的相似性表明，这些现象也可以通过与BEC的类比来理解。推广这种类比，该小组将尝试观察到一种类似于BEC的相变，在这种相变中，当交叉AOM对输入激光的随机调制增加到超过一定的临界幅度时，与中央尖峰动量谱相对应的准直输出光束突然变得不准直。

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.