“…Substituting into (1), moving to the right side, and using orthogonal polynomial expansion, we get [2,7], where N (m) is called the frequency dispersion matrix, whose elements are, Note that M (m) is proportional to the beam intensity, therefore, at very low intensity, the system is dominated solely by N (m ). This matrix is real and symmetric, which decomposes the original system into several lossless resonators with slightly difference inherent oscillation frequencies, and introduces no instability mechanism.…”