Topological polarisation states

Polarisation states are described by spin expectation values, known as Stokes parameters, the trajectories of which in a rotationally symmetric system form sphere named after Poincaré. Here, we show that broken rotational systems can exhibit distinct topological structures polarisation states. We use phase-shifter to circle (S1) , interferes with original input due phase change output state upon rotation. By rotating using rotator, become torus id="m2">S1×<mml:mi was experimentally confirmed simple setup passive optical components together Mach–Zehnder interferometer. also discuss realisations other features, such Möbius strip, trefoil knot, Hopf links, and Dirac bosons, bulk-edge correspondence.