  Heralded single-photon source (HSPS) with competitive single photon purity
and indistinguishability has become an essential resource for photonic quantum
information processing. Here, for the first time, we proposed a theoretical
regime to enhance heralded single-photons generation by multiplexing the degree
of the freedom of orbital angular momentum (OAM) of down-converted entangled
photon pairs emitted from a nonlinear crystal. Experimentally, a
proof-of-principle experiment has been performed through multiplexing three OAM
modes. We achieve a 47$\%$ enhancement in single photon rate. A second-order
autocorrelation function $g^{(2)}(0)<0.5$ ensures our multiplexed heralded
single photons with good single photon purity. We further indicate that an
OAM-multiplexed HSPS with high quality can be constructed by generating higher
dimensional entangled state and sorting them with high efficiency in OAM space.
Our avenue may approach a good HSPS with the deterministic property.

Quantum Physics;Optics