Orbital-angular-momentum-based parity-time symmetry in an optoelectronic oscillator

Parity-time (PT) symmetry provides a new technique for generating single mode oscillation in a microwave photonic oscillator (MPO). In this paper, we present a novel scheme for satisfying PT-symmetry breaking condition in a MPO with orbital angular momentum (OAM). To the best of knowledge, this is the first presentation of OAM-based PT-symmetry. Not only one PT-symmetric structure can be realized, but also multiple PT-symmetric structures can be constructed by changing the phase distribution of the OAM signal in the oscillation loop, which can enhance the sidemode suppression ratio and the stability of the oscillator.