“…is well known in the literature and finds many application in physics [22-25, 30, 57, 64, 65, 82-85, 90, 91]. It arises quite naturally in the studies of parametric oscillators [22][23][24][25]30], in the description of structured light in varying media [82][83][84][85], and in the study of non-Hermitian Hamiltonians with real spectrum [57,64,65]. The key to solve (C-1) is to consider the homogeneous linear equation q + Ω 2 (t) q = 0, (C-2) which coincides with the equation of motion for a classical parametric oscillator.…”