Quasi-flat bands in waveguide arrays
  Coupled electromagnetic waves propagating in a waveguide array are discussed. This waveguide array can be considered as one dimensional photon crystal composed from the unit cell containing three different waveguides, namely, two positive refraction index waveguides and one waveguide with negative refraction index. Spectrum of the linear modes of electromagnetic waves in this device contains the quasi-flat band. 
Andrei Maimistov
nlin.PS