Observation of second order meron polarisation textures in optical microcavities

Multicomponent Bose-Einstein condensates, quantum Hall systems, and chiral magnetic materials display twists and knots in the continuous symmetries of their order parameter, known as Skyrmions. Originally discovered as solutions to the nonlinear sigma model in quantum field theory, these vectorial excitations are quantified by a topological winding number dictating their interactions and global properties of the host system. Here, we report the first experimental observation of a stable individual second order meron, and antimeron, appearing in an electromagnetic field. These complex textures are realised by confining light into a liquid-crystal filled cavity which, through its anisotropic refractive index, provides an adjustable artificial photonic gauge field which couples the cavity photons motion to its polarisation resulting in formation of these fundamental vectorial vortex states of light. Our observations take a step towards bringing topologically robust room-temperature optical vector textures into the field of photonic information processing and storage.