  We present an optical setup for generating a sequence of light pulses in
which the orbital angular momentum (OAM) degree of freedom is correlated with
the temporal one. The setup is based on a single $q$-plate within a ring
optical resonator. By this approach, we demonstrate the generation of a train
of pulses carrying increasing values of OAM, or, alternatively, of a controlled
temporal sequence of pulses having prescribed OAM superposition states.
Finally, we exhibit an "OAM-to-time conversion" apparatus dividing different
input OAM states into different time-bins. The latter application provides a
simple approach to digital spiral spectroscopy of pulsed light.
