We present a class of waveguide arrays that is the classical analog of a
quantum harmonic oscillator where the mass and frequency depend on the
propagation distance. In these photonic lattices refractive indices and second
neighbor couplings define the mass and frequency of the analog quantum
oscillator, while first neighbor couplings are a free parameter to adjust the
model. The quantum model conserves the Ermakov-Lewis invariant, thus the
photonic crystal also posses this symmetry.Comment: 8 pages, 3 figure
