The shallow mini-band states have been clearly located in experiment in the graded periodic structure which was fabricated by the holography method. We demonstrated that the band edge folding and splitting into individual shallow levels are due to long-periodic modulation. Numerical simulations show strong slow-light effect and low secondorder dispersion of mini bands. By taking into account the non-uniform distribution of the material, the numerical results agree quite well with the experimental results. To our knowledge, this is the first instance in which shallow miniband states have been experimentally located in a graded periodic film via the holography method.
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