Figure 3. Non-cyclic evolution of degenerate photon systems in asymmetric microcavities.

(a) The polarization state of light circulating in an asymmetric tube changes from linear to elliptical, which is visualized by defining a wave-accompanying coordinate (t, d, b) frame (bottom panel). In this process, the major axes of the evolving polarization state assumes a spiral around the tube axis which is shown with respect to the laboratory coordinate frame (top panel). (b) A series of measured polarization states (red dots) in the asymmetric tubes are plotted on a Poincaré sphere, which are fitted (blue curve) based on equation (6).