The fact that a photon in a light beam can carry orbital angular momentum (OAM) in the integer multiples of ℏ has made OAM a very important degree of freedom for quantum information and quantum metrology. However, efficient techniques for generating and detecting high-dimensional OAM entangled states have been lacking, which severely limits the potential applicability of such states for real-world applications. In this talk, I will present our recently-developed techniques for efficiently generating and detecting OAM-entangled states with dimensionalities up to 200. I will also present our experimental demonstrations of a novel feature of two-photon OAM-entanglement, by which any decay of OAM entanglement due to atmospheric turbulence or otherwise can be revived simply by propagating the two photons a little further away.