Photons are weak particles that do not directly couple to magnetic fields.
However, it is possible to generate a photonic gauge field by breaking
reciprocity such that the phase of light depends on its direction of
propagation. This non-reciprocal phase indicates the presence of an effective
magnetic field for the light itself. By suitable tailoring of this phase it is
possible to demonstrate quantum effects typically associated with electrons,
and as has been recently shown, non-trivial topological properties of light.
This paper reviews dynamic modulation as a process for breaking the
time-reversal symmetry of light and generating a synthetic gauge field, and
discusses its role in topological photonics, as well as recent developments in
exploring topological photonics in higher dimensions.Comment: 20 pages, 3 figure
