  The large number of available orbital angular momentum (OAM) states of
photons provides a unique resource for many important applications in quantum
information and optical communications. However, conventional OAM switching
devices usually rely on precise parameter control and are limited by slow
switching rate and low efficiency. Here we propose a robust, fast and efficient
photonic OAM switch device based on a topological process, where photons are
adiabatically pumped to a target OAM state on demand. Such topological OAM
pumping can be realized through manipulating photons in a few degenerate main
cavities and involves only a limited number of optical elements. A large change
of OAM at $\sim 10^{q}$ can be realized with only $q$ degenerate main cavities
and at most $5q$ pumping cycles. The topological photonic OAM switch may become
a powerful device for broad applications in many different fields and motivate
novel topological design of conventional optical devices.
