“…In common non-degenerate states, it has been confirmed that the high-order HG mode can be experimentally generated under off-axis pumping with a sufficiently large off-axis displacement [35,38]. Whereas in degenerate states, it has been theoretically and experimentally confirmed that the emission mode can be characterized by the quantum coherent states with SU(2) Lie algebra [33]: where M + 1 stands for the number of HG modes in family of ψ (HG) n 0 +Q·K,0,s 0 −P ·K (x, y, z) with K = 1, 2, 3, · · · , which constitute a family of frequency-degenerate modes, where n 0 and s 0 represent the minimum transverse and maximum longitudinal orders in the degenerate family respectively. Note that all the discussion corresponding to the off-axis pumping with (∆x, 0) can be applied to the case of (0, ∆y) for the degenerate family in terms of ψ (HG) 0,m 0 +Q·K,s 0 −P ·K (x, y, z).…”