  Genuine random numbers can be produced beyond a shadow of doubt through the
intrinsic randomness provided by quantum mechanics theory. While many degrees
of freedom have been investigated for randomness generation, not adequate
attention has been paid to the orbital angular momentum of light. In this work,
we present a quantum random number generator based on the intrinsic randomness
inherited from the superposition of orbital angular momentum modes caused by
the crosstalk inside a ring-core fiber. We studied two possible cases: a first
one, device-dependent, where the system is trusted, and a second one,
semi-device-independent, where the adversary can control the measurements. We
experimentally realized the former, extracted randomness, and, after privacy
amplification, we achieved a generation rate higher than 10 Mbit/s. In
addition, we presented a possible realization of the semi-device-independent
protocol, using a newly introduced integrated silicon photonic chip. Our work
can be considered as a starting point for novel investigations of quantum
random number generators based on the orbital angular momentum of light.
