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The non-locality of optical properties of gradient dielectric nanofilms, stipulated by smooth spatial distributions of refractive index, is shown to create the peculiar plasma-like dispersion of non-polar dielectric films, determined by the shapes and sizes of these distributions. Gradient all-dielectric nanostructures, characterized by the artificial heterogeneity-induced nonlocal dispersion and providing the broadband antireflection tunneling regime of energy transport in the visible and infrared ranges, are designed and tested. The wave energy flow in these structures is supported due to interference of evanescent and antievanescent modes formed by the non-Fresnel reflections of these modes on the discontinuities of gradient of refractive index on the boundaries of adjacent nanofilms. The transmittance spectra of these structures in the visible and infrared ranges, characterized by strong dispersion nearby the red edge of visible range, almost constant high transmittance in the near infrared range and weak dependence of tunneling energy flow upon the multilayer structure thickness, are calculated; the experimental verifications of these effects are presented. The perspectives to use the tunneling of light in gradient media for reconsideration of Hartman paradox are shown. Potential of periodical gradient all-dielectric nanostructures for optimized design of optical dispersive elements and broadband antireflection coatings for the visible and IR spectral range, respectively, is discussed.

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